Systems and methods for detecting region of interset in image

ABSTRACT

The present disclosure provides a region of interest (ROI) detection system. The system may be configured to acquire a target image and an ROI detection model, and perform ROI detection on the target image by applying the ROI detection model to the target image. The ROI detection model may be a trained cascaded neural network including a plurality of sequentially connected trained models. The plurality of trained models may include a trained first model and at least one trained second model downstream to the trained first model in the trained cascaded neural network. The plurality of trained models may be sequentially trained. Each of the trained second model may be trained using a plurality of training samples determined based on one or more trained models of the plurality of trained models generated before the generation of the trained second model.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/600,960, filed on Oct. 14, 2019, which claims priority to ChinesePatent Application No. 201811417230.2, filed on Nov. 26, 2018, thecontents of each of which are hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure generally relates to image processing, and moreparticularly, relates to systems and methods for detecting a region ofinterest (ROI) in an image using a machine learning technique.

BACKGROUND

Computer-aided detection (CAD) techniques are widely used in ROIdetection in various areas, such as medical imaging and diagnosticradiology. For example, the CAD technique is often used to detect asuspicious lesion from a medical image to provide a basis for medicaldiagnosis and/or treatment. Recently, machine learning has promoted thedevelopment of CAD technology. For example, an ROI detection model maybe trained using a machine learning technique and applied to a targetimage to automatically detect one or more ROIs in the target image. Atpresent, an ROI detection model is usually designed for detecting aparticular type of ROI (e.g., a pulmonary nodule) and/or an ROI having aparticular size, which may have limited accuracy and/or efficiency inROI detection. Therefore, it is desirable to provide effective systemsand methods for generating an ROI detection model and for using the ROIdetection model to detect an ROI in a target image.

SUMMARY

According to one aspect of the present disclosure, an ROI detectionsystem is provided. The system may include at least one storage mediumstoring a set of instructions, and at least one processor incommunication with the at least one storage medium. When executing theinstructions, the at least one processor may be configured to direct thesystem to perform the following operations. The at least one processormay be configured to direct the system to acquire a target image and anROI detection model. The at least one processor may be configured todirect the system to perform ROI detection on the target image byapplying the ROI detection model to the target image. The ROI detectionmodel may be a trained cascaded neural network including a plurality ofsequentially connected trained models. The plurality of trained modelsmay include a trained first model and at least one trained second modeldownstream to the trained first model in the trained cascaded neuralnetwork. The plurality of trained models may be sequentially trained.Each of the trained second model may be trained using a plurality oftraining samples determined based on one or more trained models of theplurality of trained models generated before the generation of thetrained second model.

In some embodiments, each of the plurality of trained models may beconfigured to generate an output in response to an input of the trainedmodel. The input to the trained first model may include the targetimage. The input to each of the at least one trained second model mayinclude an output of a previous trained model connected to the trainedsecond model. To perform an ROI detection on the target image byapplying the ROI detection model to the target image, the at least oneprocessor may be further configured to direct the system to obtain anoutput of a last trained model of the plurality of trained models. Theat least one processor may be configured to direct the system todetermine one or more ROIs in the target image based on the output ofthe last trained model.

In some embodiments, each of the plurality of trained models may beconfigured to generate an output in response to an input of the trainedmodel. The input to each trained model may include the target image. Toperform an ROI detection on the target image by applying the ROIdetection model to the target image, the at least one processor may befurther configured to direct the system to obtain an output of each ofthe plurality of trained models, and determine one or more ROIs in thetarget image based on the outputs of the plurality of trained models.

In some embodiments, the target image may include a plurality of targetpixels. The output of each trained model may include a first preliminaryprobability map. The first preliminary probability map may include aplurality of first preliminary probability values of the plurality oftarget pixels. Each of the plurality of first preliminary probabilityvalues may be indicative of a preliminary probability that acorresponding target pixel belongs to an ROI of the target image. Todetermine one or more ROIs in the target image based on the outputs ofthe plurality of trained models, the at least one processor may be alsoconfigured to direct the system to determine a first target probabilitymap including a plurality of first target probability values of theplurality of target pixels based on the first preliminary probabilitymaps. Each of the plurality of first target probability values may beindicative of a target probability that a corresponding target pixelbelongs to an ROI of the target image. The at least one processor may befurther configured to direct the system to determine the one or moreROIs of the target image based on the first target probability map.

In some embodiments, the target image may include a plurality of targetpixels. Each of the target pixels may have a plurality of target anchorboxes, each of the target anchor boxes enclosing the target pixel andrepresenting a candidate ROI enclosing the target pixel. The output ofeach trained model may include a second preliminary probability map anda target regression map. The second preliminary probability map mayinclude a plurality of second preliminary probability values of theplurality of target anchor boxes. Each second preliminary probabilityvalue of a target anchor box may be indicative of a preliminaryprobability that a corresponding candidate ROI is an ROI of the targetimage. The target regression map may include least one target locationparameter of at least one of the plurality of target anchor boxes. Eachtarget location parameter of a target anchor box may be indicative of aposition or a size of the target anchor box relative to an ROI of thetarget image. To determine one or more ROIs in the target image based onthe outputs of the plurality of trained models, the at least oneprocessor may be also configured to direct the system to determine asecond target probability map including a plurality of second targetprobability values of the plurality of target anchor boxes based on thesecond preliminary probability maps of the plurality of trained models.Each second target probability value of a target anchor box may beindicative of a target probability that a corresponding candidate ROI isan ROI of the target image. The at least one processor may be furtherconfigured to direct the system to determine a plurality of preliminaryROIs of the target image based on the target regression map of a lasttrained model of the plurality of trained models and the second targetprobability map, and determine the one or more ROIs of the target imagebased on the plurality of preliminary ROIs.

In some embodiments, the at least one processor may be furtherconfigured to direct the system to determine the one or more ROIs of thetarget image by performing a non-maximum suppressing on the plurality ofpreliminary ROIs.

In some embodiments, at least one trained model of the plurality oftrained models may include a multi-scale trained model configured toperform ROI detection at a plurality of resolution levels.

In some embodiments, the multi-scale trained model may include aplurality of sequentially connected layers each of which corresponds toone of the plurality of resolution levels. The plurality of layers mayinclude a first layer, a last layer, and one or more middle layersbetween the first layer and the last layer. At least one layer of theplurality of layers other than the last layer may be connected to a nextlayer via a downsampling path. At least one layer of the plurality oflayers other than the first layer may be connected to a previous layervia an upsampling path.

According to another aspect of the present disclosure, a system forgenerating an ROI detection model is provided. The system may include atleast one storage medium storing a set of instructions, and at least oneprocessor in communication with the at least one storage medium. Whenexecuting the instructions, the at least one processor may be configuredto direct the system to perform the following operations. The at leastone processor may be configured to direct the system to acquire aplurality of training images. Each of the plurality of training imagesmay be annotated with one or more ROIs. The at least one processor maybe configured to direct the system to generate an ROI detection model bytraining a cascaded neural network using the plurality of trainingimages. The cascaded neural network may include a plurality ofsequentially connected models. The plurality of models may include afirst model and at least one second model downstream to the first modelin the cascaded neural network. The training the cascaded neural networkmay include sequentially training the plurality of models. The trainingeach of the plurality of models may include determine a plurality oftraining samples of the model based at least in part on the plurality oftraining images, and generating a trained model by training the modelusing the plurality of training samples of the model. The plurality oftraining samples of each of the at least one second model may bedetermined further based on one or more trained models generated beforethe training of the second model.

In some embodiments, the determining a plurality of training samples ofthe first model may include determining a plurality of first negativesamples of the first model and a plurality of positive samples based onthe plurality of training images. Each of the plurality of firstnegative samples may be indicative of at least a portion of a non-ROI inthe plurality of training images. Each of the plurality of positivesamples may be indicative of at least a portion of the ROIs in theplurality of training images. The determining a plurality of trainingsamples of the first model may also include designating the plurality offirst negative samples and the plurality of positive samples as thetraining samples of the first model.

In some embodiments, the determining a plurality of first negativesamples of the first model and a plurality of positive samples mayinclude designating a plurality of pixels in the ROIs as the pluralityof positive samples, and designating a plurality of pixels outside theROIs as the plurality of first negative samples.

In some embodiments, the determining a plurality of first negativesamples of the first model and a plurality of positive samples mayinclude for each of a plurality of pixels in the plurality of trainingimages, defining one or more anchor boxes enclosing the pixel, each ofthe one or more anchor boxes representing a candidate ROI enclosing thepixel. The determining a plurality of first negative samples of thefirst model and a plurality of positive samples may include comparingthe anchor boxes with the ROIs of the plurality of training images togenerate a comparison result. The determining a plurality of firstnegative samples of the first model and a plurality of positive samplesmay also include determining the plurality of first negative samples andthe plurality of positive samples among the anchor boxes based on thecomparison result.

In some embodiments, a ratio of a count of the plurality of positivesamples to a count of the plurality of first negative samples may beequal to or greater than a threshold ratio. The threshold ratio may besubstantially equal to 0.2.

In some embodiments, for each of the at least one second model, thedetermining the training samples for each of the at least one secondmodel may include determining a plurality of predicted positive samplesrepresenting a plurality of predicted ROIs in the plurality of trainingimages by applying the one or more trained models generated before thetraining of the second model to the plurality of training images. Thedetermining the training samples for each of the at least one secondmodel may include identifying one or more false positive samples amongthe plurality of predicted positive samples, and determining a pluralityof second negative samples of the second model. The plurality of secondnegative samples may include at least a portion of the one or more falsepositive samples. The determining the training samples for each of theat least one second model may further include designating the pluralityof second negative samples and the plurality of positive samples as thetraining samples of the second model.

In some embodiments, for each of the at least one second model, thetraining each of the plurality of models may further include determiningwhether a termination condition is satisfied. The training each of theplurality of models may further include, upon a determination that thetermination condition is satisfied, designating a trained cascadedneural network as the ROI detection model. The trained cascaded neuralnetwork may include the trained second model and the one or more trainedmodels generated before the training of the second model.

In some embodiments, at least one model of the plurality of models mayinclude a multi-scale model configured to perform ROI detection at aplurality of resolution levels.

In some embodiments, the multi-scale model may include a plurality ofsequentially connected layers. The plurality of layers may include afirst layer, a last layer, and one or more middle layers between thefirst layer and the last layer. At least one layer of the plurality oflayers other than the last layer may be connected to a next layer via adownsampling path. At least one layer of the plurality of layers otherthan the first layer may be connected to a previous layer via anupsampling path.

In some embodiments, at least one of the one or more middle layers mayinclude a first block, a second block, and a connection componentconnecting the first block and the second block.

In some embodiments, the ROI detection model may be configured toperform lesion detection on a target image.

According to still another aspect of the present disclosure, anon-transitory computer-readable storage medium including instructionsis provided. When executed by at least one processor of an ROI detectionsystem, the instructions causes the system to perform a method. Themethod may include acquiring a target image and an ROI detection model,and performing ROI detection on the target image by applying the ROIdetection model to the target image. The ROI detection model may be atrained cascaded neural network including a plurality of sequentiallyconnected trained models. The plurality of trained models may include atrained first model and at least one trained second model downstream tothe trained first model in the trained cascaded neural network. Theplurality of trained models may be sequentially trained. Each of thetrained second model may be trained using a plurality of trainingsamples determined based on one or more trained models of the pluralityof trained models generated before the generation of the trained secondmodel.

Additional features will be set forth in part in the description whichfollows, and in part will become apparent to those skilled in the artupon examination of the following and the accompanying drawings or maybe learned by production or operation of the examples. The features ofthe present disclosure may be realized and attained by practice or useof various aspects of the methodologies, instrumentalities, andcombinations set forth in the detailed examples discussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is further described in terms of exemplaryembodiments. These exemplary embodiments are described in detail withreference to the drawings. The drawings are not to scale. Theseembodiments are non-limiting exemplary embodiments, in which likereference numerals represent similar structures throughout the severalviews of the drawings, and wherein:

FIG. 1 is a schematic diagram illustrating an exemplary imaging systemaccording to some embodiments of the present disclosure;

FIG. 2 is a schematic diagram illustrating exemplary hardware and/orsoftware components of a computing device according to some embodimentsof the present disclosure;

FIG. 3 is a schematic diagram illustrating exemplary hardware and/orsoftware components of a mobile device according to some embodiments ofthe present disclosure;

FIGS. 4A and 4B are block diagrams illustrating exemplary processingdevices according to some embodiments of the present disclosure;

FIG. 5 is a flowchart illustrating an exemplary process for generatingan ROI detection model according to some embodiments of the presentdisclosure;

FIG. 6A is a flowchart illustrating an exemplary process for determininga plurality of training samples of a first model of a cascaded neuralnetwork according to some embodiments of the present disclosure;

FIG. 6B is a flowchart illustrating an exemplary process for determininga plurality of training samples of a second model of a cascaded neuralnetwork according to some embodiments of the present disclosure;

FIG. 7 is a flowchart illustrating an exemplary process for generating atrained model by training a model using a plurality of training samplesof the model according to some embodiments of the present disclosure;

FIG. 8 is a flowchart illustrating an exemplary process for performingROI detection on a target image using an ROI detection model accordingto some embodiments of the present disclosure;

FIG. 9 is a schematic diagram illustrating an exemplary ROI detectionmodel according to some embodiments of the present disclosure;

FIG. 10 is a schematic diagram illustrating an exemplary process forperforming lesion detection on a target image using a lesion detectionmodel according to some embodiments of the present disclosure;

FIG. 11 is a schematic diagram illustrating an exemplary single-scaleROI detection model according to some embodiments of the presentdisclosure;

FIG. 12 is a schematic diagram illustrating an exemplary multi-scale ROIdetection model according to some embodiments of the present disclosure;and

FIG. 13 is a schematic diagram illustrating an exemplary CNN modelaccording to some embodiments of the present disclosure.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth by way of examples in order to provide a thorough understanding ofthe relevant disclosure. However, it should be apparent to those skilledin the art that the present disclosure may be practiced without suchdetails. In other instances, well-known methods, procedures, systems,components, and/or circuitry have been described at a relativelyhigh-level, without detail, in order to avoid unnecessarily obscuringaspects of the present disclosure. Various modifications to thedisclosed embodiments will be readily apparent to those skilled in theart, and the general principles defined herein may be applied to otherembodiments and applications without departing from the spirit and scopeof the present disclosure. Thus, the present disclosure is not limitedto the embodiments shown, but to be accorded the widest scope consistentwith the claims.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprise,”“comprises,” and/or “comprising,” “include,” “includes,” and/or“including,” when used in this specification, specify the presence ofstated features, integers, steps, operations, elements, and/orcomponents, but do not preclude the presence or addition of one or moreother features, integers, steps, operations, elements, components,and/or groups thereof.

It will be understood that the term “system,” “engine,” “unit,”“module,” and/or “block” used herein are one method to distinguishdifferent components, elements, parts, section or assembly of differentlevel in ascending order. However, the terms may be displaced by anotherexpression if they achieve the same purpose.

Generally, the word “module,” “unit,” or “block,” as used herein, refersto logic embodied in hardware or firmware, or to a collection ofsoftware instructions. A module, a unit, or a block described herein maybe implemented as software and/or hardware and may be stored in any typeof non-transitory computer-readable medium or another storage device. Insome embodiments, a software module/unit/block may be compiled andlinked into an executable program. It will be appreciated that softwaremodules can be callable from other modules/units/blocks or fromthemselves, and/or may be invoked in response to detected events orinterrupts. Software modules/units/blocks configured for execution oncomputing devices (e.g., processor 210 as illustrated in FIG. 2 ) may beprovided on a computer-readable medium, such as a compact disc, adigital video disc, a flash drive, a magnetic disc, or any othertangible medium, or as a digital download (and can be originally storedin a compressed or installable format that needs installation,decompression, or decryption prior to execution). Such software code maybe stored, partially or fully, on a storage device of the executingcomputing device, for execution by the computing device. Softwareinstructions may be embedded in firmware, such as an EPROM. It will befurther appreciated that hardware modules/units/blocks may be includedin connected logic components, such as gates and flip-flops, and/or canbe included of programmable units, such as programmable gate arrays orprocessors. The modules/units/blocks or computing device functionalitydescribed herein may be implemented as software modules/units/blocks,but may be represented in hardware or firmware. In general, themodules/units/blocks described herein refer to logicalmodules/units/blocks that may be combined with othermodules/units/blocks or divided into sub-modules/sub-units/sub-blocksdespite their physical organization or storage. The description may beapplicable to a system, an engine, or a portion thereof.

It will be understood that when a unit, engine, module or block isreferred to as being “on,” “connected to,” or “coupled to,” anotherunit, engine, module, or block, it may be directly on, connected orcoupled to, or communicate with the other unit, engine, module, orblock, or an intervening unit, engine, module, or block may be present,unless the context clearly indicates otherwise. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items. The term “image” in the present disclosure isused to collectively refer to image data (e.g., scan data, projectiondata) and/or images of various forms, including a two-dimensional (2D)image, a three-dimensional (3D) image, a four-dimensional (4D), etc. Theterm “pixel” and “voxel” in the present disclosure are usedinterchangeably to refer to an element of an image.

These and other features, and characteristics of the present disclosure,as well as the methods of operation and functions of the relatedelements of structure and the combination of parts and economies ofmanufacture, may become more apparent upon consideration of thefollowing description with reference to the accompanying drawings, allof which form a part of this disclosure. It is to be expresslyunderstood, however, that the drawings are for the purpose ofillustration and description only and are not intended to limit thescope of the present disclosure. It is understood that the drawings arenot to scale.

Provided herein are systems and methods for non-invasive biomedicalimaging, such as for disease diagnostic or research purposes. In someembodiments, the systems may include a single modality imaging systemand/or a multi-modality imaging system. The single modality imagingsystem may include, for example, an ultrasound imaging system, an X-rayimaging system, an computed tomography (CT) system, a magnetic resonanceimaging (MRI) system, an ultrasonography system, a positron emissiontomography (PET) system, an optical coherence tomography (OCT) imagingsystem, an ultrasound (US) imaging system, an intravascular ultrasound(IVUS) imaging system, a near infrared spectroscopy (NIRS) imagingsystem, or the like, or any combination thereof. The multi-modalityimaging system may include, for example, an X-ray imaging-magneticresonance imaging (X-ray-MRI) system, a positron emissiontomography-X-ray imaging (PET-X-ray) system, a single photon emissioncomputed tomography-magnetic resonance imaging (SPECT-MRI) system, apositron emission tomography-computed tomography (PET-CT) system, aC-arm system, a digital subtraction angiography-magnetic resonanceimaging (DSA-MRI) system, etc. It should be noted that the imagingsystem described below is merely provided for illustration purposes, andnot intended to limit the scope of the present disclosure.

The term “imaging modality” or “modality” as used herein broadly refersto an imaging method or technology that gathers, generates, processes,and/or analyzes imaging information of an object. The object may includea biological object and/or a non-biological object. The biologicalobject may be a human being, an animal, a plant, or a portion thereof(e.g., a cell, a tissue, an organ, etc.). In some embodiments, theobject may be a man-made composition of organic and/or inorganic mattersthat are with or without life.

Moreover, while the systems and methods disclosed in the presentdisclosure are described primarily regarding determining an ROI in animage in a medical imaging system. It should be understood that this isonly one exemplary embodiment. The systems and methods of the presentdisclosure may be applied to any other kind of systems. For example, thesystems and methods of the present disclosure may be applied to detectROIs in images acquired in different scenarios and/or for differentpurposes (e.g., safety monitoring, filming, or photography) and/or bydifferent image acquisition devices (e.g., a digital camera, an analogcamera, or a scanner).

An aspect of the present disclosure relates to systems and methods forgenerating an ROI detection model. The systems and methods may acquire aplurality of training images, each training image being annotated withone or more ROIs. The systems and methods may also generate an ROIdetection model by training a cascaded neural network using the trainingimages. The cascaded neural network may include a plurality ofsequentially connected models. The models may be sequentially trained inthe training of the cascaded neural network. For each model, the systemsand methods may determine a plurality of training samples of the model,and train the model using the corresponding training samples.

According to some embodiments of the present disclosure, the trainingsamples of a specific model of a series of models (e.g., a plurality ofsecond models described elsewhere in the present disclosure) may bedetermined based on the one or more trained models generated before thetraining of the specific model. For example, the training samples of aspecific model may include one or more false positive samples predictedby the trained model(s) generated before the training of the specificmodel. In this way, the trained specific model may learn one or morefeatures of the false positive samples and have a higher accuracy indistinguishing a non-ROI from an ROI than the model(s) trained usingtraining samples that do not include any false positive sample, which inturn may improve the accuracy of the ROI detection model. In addition,in some embodiments, the performance of the ROI detection model may befurther improved by incorporating one or more multi-scale trained modelsconfigured to perform ROI detection at a plurality of resolution levels,so that the ROI detection model may be applied to detect ROIs of varioussizes.

FIG. 1 is a schematic diagram illustrating an exemplary imaging system100 according to some embodiments of the present disclosure. As shown,the imaging system 100 may include an imaging device 110, a network 120,one or more terminals 130, a processing device 140, and a storage device150. In some embodiments, the imaging device 110, the terminal(s) 130,the processing device 140, and/or the storage device 150 may beconnected to and/or communicate with each other via a wirelessconnection (e.g., the network 120), a wired connection, or a combinationthereof. The connection between the components of the imaging system 100may be variable. Merely by way of example, the imaging device 110 may beconnected to the processing device 140 through the network 120, asillustrated in FIG. 1 . As another example, the imaging device 110 maybe connected to the processing device 140 directly. As a furtherexample, the storage device 150 may be connected to the processingdevice 140 through the network 120, as illustrated in FIG. 1 , orconnected to the processing device 140 directly. As still a furtherexample, a terminal 130 may be connected to the processing device 140through the network 120, as illustrated in FIG. 1 , or connected to theprocessing device 140 directly.

The imaging device 110 may generate or provide image data related to anobject via scanning the object. In some embodiments, the object mayinclude a biological object and/or a non-biological object. For example,the object may include a specific portion of a body, such as a head, athorax, an abdomen, or the like, or a combination thereof. In someembodiments, the imaging device 110 may include a single-modalityscanner (e.g., a CT scanner) and/or multi-modality scanner (e.g., aPET-CT scanner) as described elsewhere in this disclosure. In someembodiments, the image data relating to the object may includeprojection data, one or more images of the object, etc. The projectiondata may include raw data generated by the imaging device 110 byscanning the object and/or data generated by a forward projection on animage of the object.

In some embodiments, the imaging device 110 may include a gantry 111, adetector 112, a detecting region 113, a scanning table 114, and aradioactive scanning source 115. The gantry 111 may support the detector112 and the radioactive scanning source 115. The object may be placed onthe scanning table 114 to be scanned. The radioactive scanning source115 may emit radioactive rays to the object. The radiation may include aparticle ray, a photon ray, or the like, or a combination thereof. Insome embodiments, the radiation may include a plurality of radiationparticles (e.g., neutrons, protons, electron, p-mesons, heavy ions), aplurality of radiation photons (e.g., X-ray, a y-ray, ultraviolet,laser), or the like, or a combination thereof. The detector 112 maydetect radiations and/or radiation events (e.g., gamma photons) emittedfrom the detecting region 113. In some embodiments, the detector 112 mayinclude a plurality of detector units. The detector units may include ascintillation detector (e.g., a cesium iodide detector) or a gasdetector. The detector unit may be a single-row detector or a multi-rowsdetector.

The network 120 may include any suitable network that can facilitate theexchange of information and/or data for the imaging system 100. In someembodiments, one or more components of the imaging system 100 (e.g., theimaging device 110, the processing device 140, the storage device 150,the terminal(s) 130) may communicate information and/or data with one ormore other components of the imaging system 100 via the network 120. Forexample, the processing device 140 may obtain image data from theimaging device 110 via the network 120. As another example, theprocessing device 140 may obtain user instruction(s) from theterminal(s) 130 via the network 120.

The network 120 may be or include a public network (e.g., the Internet),a private network (e.g., a local area network (LAN)), a wired network, awireless network (e.g., an 802.11 network, a Wi-Fi network), a framerelay network, a virtual private network (VPN), a satellite network, atelephone network, routers, hubs, switches, server computers, and/or anycombination thereof. For example, the network 120 may include a cablenetwork, a wireline network, a fiber-optic network, a telecommunicationsnetwork, an intranet, a wireless local area network (WLAN), ametropolitan area network (MAN), a public telephone switched network(PSTN), a Bluetooth™ network, a ZigBee™ network, a near fieldcommunication (NFC) network, or the like, or any combination thereof. Insome embodiments, the network 120 may include one or more network accesspoints. For example, the network 120 may include wired and/or wirelessnetwork access points such as base stations and/or internet exchangepoints through which one or more components of the imaging system 100may be connected to the network 120 to exchange data and/or information.

The terminal(s) 130 may be connected to and/or communicate with theimaging device 110, the processing device 140, and/or the storage device150. For example, the terminal(s) 130 may display an image annotatedwith one or more ROIs, wherein the ROI(s) in the image may be detectedautomatically by an ROI detection model. In some embodiments, theterminal(s) 130 may include a mobile device 131, a tablet computer 132,a laptop computer 133, or the like, or any combination thereof. Forexample, the mobile device 131 may include a mobile phone, a personaldigital assistant (PDA), a gaming device, a navigation device, a pointof sale (POS) device, a laptop, a tablet computer, a desktop, or thelike, or any combination thereof. In some embodiments, the terminal(s)130 may include an input device, an output device, etc. In someembodiments, the terminal(s) 130 may be part of the processing device140.

The processing device 140 may process data and/or information obtainedfrom the imaging device 110, the storage device 150, the terminal(s)130, or other components of the imaging system 100. In some embodiments,the processing device 140 may be a single server or a server group. Theserver group may be centralized or distributed. For example, theprocessing device 140 may process a plurality of training images toselect a plurality of training samples for training an ROI detectionmodel. The processing device 140 may further generate the ROI detectionmodel by training a model using the training samples. As anotherexample, the processing device 140 may apply the ROI detection model toa target image to perform ROI detection in the target image. In someembodiments, the training samples and/or the ROI detection model may begenerated by a processing device, while the application of the ROIdetection model may be performed on a different processing device. Insome embodiments, the training samples and/or the ROI detection modelmay be generated by a processing device of a system different than theimaging system 100 or a server different than the processing device 140on which the application of ROI detection model is performed. Forinstance, the training samples and/or the ROI detection model may begenerated by a first system of a vendor who provides and/or maintainssuch an ROI detection model, while ROI detection on a target image basedon the provided ROI detection model may be performed on a second systemof a client of the vendor. In some embodiments, the application of theROI detection model may be performed online in response to a request forROI detection in a target image. In some embodiments, the trainingsamples and/or the ROI detection model may be determined or generatedoffline.

In some embodiments, the processing device 140 may be local to or remotefrom the imaging system 100. For example, the processing device 140 mayaccess information and/or data from the imaging device 110, the storagedevice 150, and/or the terminal(s) 130 via the network 120. As anotherexample, the processing device 140 may be directly connected to theimaging device 110, the terminal(s) 130, and/or the storage device 150to access information and/or data. In some embodiments, the processingdevice 140 may be implemented on a cloud platform. For example, thecloud platform may include a private cloud, a public cloud, a hybridcloud, a community cloud, a distributed cloud, an inter-cloud, amulti-cloud, or the like, or a combination thereof. In some embodiments,the processing device 140 may be implemented by a computing device 200having one or more components as described in connection with FIG. 2 .

In some embodiments, the processing device 140 may include one or moreprocessors (e.g., single-core processor(s) or multi-core processor(s)).Merely by way of example, the processing device 140 may include acentral processing unit (CPU), an application-specific integratedcircuit (ASIC), an application-specific instruction-set processor(ASIP), a graphics processing unit (GPU), a physics processing unit(PPU), a digital signal processor (DSP), a field-programmable gate array(FPGA), a programmable logic device (PLD), a controller, amicrocontroller unit, a reduced instruction-set computer (RISC), amicroprocessor, or the like, or any combination thereof.

The storage device 150 may store data, instructions, and/or any otherinformation. In some embodiments, the storage device 150 may store dataobtained from the processing device 140, the terminal(s) 130, and/or theimaging device 110. In some embodiments, the storage device 150 maystore data and/or instructions that the processing device 140 mayexecute or use to perform exemplary methods described in the presentdisclosure. In some embodiments, the storage device 150 may include amass storage device, a removable storage device, a volatileread-and-write memory, a read-only memory (ROM), or the like, or anycombination thereof. Exemplary mass storage devices may include amagnetic disk, an optical disk, a solid-state drive, etc. Exemplaryremovable storage devices may include a flash drive, a floppy disk, anoptical disk, a memory card, a zip disk, a magnetic tape, etc. Exemplaryvolatile read-and-write memory may include a random access memory (RAM).Exemplary RAM may include a dynamic RAM (DRAM), a double date ratesynchronous dynamic RAM (DDR SDRAM), a static RAM (SRAM), a thyristorRAM (T-RAM), and a zero-capacitor RAM (Z-RAM), etc. Exemplary ROM mayinclude a mask ROM (MROM), a programmable ROM (PROM), an erasableprogrammable ROM (EPROM), an electrically erasable programmable ROM(EEPROM), a compact disk ROM (CD-ROM), and a digital versatile disk ROM,etc. In some embodiments, the storage device 150 may be implemented on acloud platform as described elsewhere in the disclosure.

In some embodiments, the storage device 150 may be connected to thenetwork 120 to communicate with one or more other components of theimaging system 100 (e.g., the processing device 140, the terminal(s)130). One or more components of the imaging system 100 may access thedata or instructions stored in the storage device 150 via the network120. In some embodiments, the storage device 150 may be part of theprocessing device 140.

It should be noted that the above description of the imaging system 100is intended to be illustrative, and not to limit the scope of thepresent disclosure. Many alternatives, modifications, and variationswill be apparent to those skilled in the art. The features, structures,methods, and other characteristics of the exemplary embodimentsdescribed herein may be combined in various ways to obtain additionaland/or alternative exemplary embodiments. For example, the imagingsystem 100 may include one or more additional components. Additionallyor alternatively, one or more components of the imaging system 100described above may be omitted. As another example, two or morecomponents of the imaging system 100 may be integrated into a singlecomponent.

FIG. 2 is a schematic diagram illustrating exemplary hardware and/orsoftware components of a computing device 200 according to someembodiments of the present disclosure. The computing device 200 may beused to implement any component of the imaging system 100 as describedherein. For example, the processing device 140 and/or the terminal 130may be implemented on the computing device 200, respectively, via itshardware, software program, firmware, or a combination thereof. Althoughonly one such computing device is shown, for convenience, the computerfunctions relating to the imaging system 100 as described herein may beimplemented in a distributed fashion on a number of similar platforms,to distribute the processing load. As illustrated in FIG. 2 , thecomputing device 200 may include a processor 210, a storage 220, aninput/output (I/O) 230, and a communication port 240.

The processor 210 may execute computer instructions (e.g., program code)and perform functions of the processing device 140 in accordance withtechniques described herein. The computer instructions may include, forexample, routines, programs, objects, components, data structures,procedures, modules, and functions, which perform particular functionsdescribed herein. For example, the processor 210 may process image dataobtained from the imaging device 110, the terminal(s) 130, the storagedevice 150, and/or any other component of the imaging system 100. Insome embodiments, the processor 210 may include one or more hardwareprocessors, such as a microcontroller, a microprocessor, a reducedinstruction set computer (RISC), an application specific integratedcircuits (ASICs), an application-specific instruction-set processor(ASIP), a central processing unit (CPU), a graphics processing unit(GPU), a physics processing unit (PPU), a microcontroller unit, adigital signal processor (DSP), a field programmable gate array (FPGA),an advanced RISC machine (ARM), a programmable logic device (PLD), anycircuit or processor capable of executing one or more functions, or thelike, or any combinations thereof.

Merely for illustration, only one processor is described in thecomputing device 200. However, it should be noted that the computingdevice 200 in the present disclosure may also include multipleprocessors, thus operations and/or method operations that are performedby one processor as described in the present disclosure may also bejointly or separately performed by the multiple processors. For example,if in the present disclosure the processor of the computing device 200executes both operation A and operation B, it should be understood thatoperation A and operation B may also be performed by two or moredifferent processors jointly or separately in the computing device 200(e.g., a first processor executes operation A and a second processorexecutes operation B, or the first and second processors jointly executeoperations A and B).

The storage 220 may store data/information obtained from the imagingdevice 110, the terminal(s) 130, the storage device 150, and/or anyother component of the imaging system 100. In some embodiments, thestorage 220 may include a mass storage device, a removable storagedevice, a volatile read-and-write memory, a read-only memory (ROM), orthe like, or any combination thereof. In some embodiments, the storage220 may store one or more programs and/or instructions to performexemplary methods described in the present disclosure. For example, thestorage 220 may store a program for the processing device 140 to executeto generate an ROI detection model.

The I/O 230 may input and/or output signals, data, information, etc. Insome embodiments, the I/O 230 may enable a user interaction with theprocessing device 140. In some embodiments, the I/O 230 may include aninput device and an output device. The input device may includealphanumeric and other keys that may be input via a keyboard, a touchscreen (for example, with haptics or tactile feedback), a speech input,an eye tracking input, a brain monitoring system, or any othercomparable input mechanism. The input information received through theinput device may be transmitted to another component (e.g., theprocessing device 140) via, for example, a bus, for further processing.Other types of the input device may include a cursor control device,such as a mouse, a trackball, or cursor direction keys, etc. The outputdevice may include a display (e.g., a liquid crystal display (LCD), alight-emitting diode (LED)-based display, a flat panel display, a curvedscreen, a television device, a cathode ray tube (CRT), a touch screen),a speaker, a printer, or the like, or a combination thereof.

The communication port 240 may be connected to a network (e.g., thenetwork 120) to facilitate data communications. The communication port240 may establish connections between the processing device 140 and theimaging device 110, the terminal(s) 130, and/or the storage device 150.The connection may be a wired connection, a wireless connection, anyother communication connection that can enable data transmission and/orreception, and/or any combination of these connections. The wiredconnection may include, for example, an electrical cable, an opticalcable, a telephone wire, or the like, or any combination thereof. Thewireless connection may include, for example, a Bluetooth™ link, aWi-Fi™ link, a WiMax™ link, a WLAN link, a ZigBee™ link, a mobilenetwork link (e.g., 3G, 4G, 5G), or the like, or a combination thereof.In some embodiments, the communication port 240 may be and/or include astandardized communication port, such as RS232, RS485, etc. In someembodiments, the communication port 240 may be a specially designedcommunication port. For example, the communication port 240 may bedesigned in accordance with the digital imaging and communications inmedicine (DICOM) protocol.

FIG. 3 is a schematic diagram illustrating exemplary hardware and/orsoftware components of a mobile device 300 according to some embodimentsof the present disclosure. In some embodiments, one or more components(e.g., a terminal 130 and/or the processing device 140) of the imagingsystem 100 may be implemented on the mobile device 300.

As illustrated in FIG. 3 , the mobile device 300 may include acommunication platform 310, a display 320, a graphics processing unit(GPU) 330, a central processing unit (CPU) 340, an I/O 350, a memory360, and a storage 390. In some embodiments, any other suitablecomponent, including but not limited to a system bus or a controller(not shown), may also be included in the mobile device 300. In someembodiments, a mobile operating system 370 (e.g., iOS™, Android™,Windows Phone™) and one or more applications 380 may be loaded into thememory 360 from the storage 390 in order to be executed by the CPU 340.The applications 380 may include a browser or any other suitable mobileapps for receiving and rendering information relating to imageprocessing or other information from the processing device 140. Userinteractions with the information stream may be achieved via the I/O 350and provided to the processing device 140 and/or other components of theimaging system 100 via the network 120.

To implement various modules, units, and their functionalities describedin the present disclosure, computer hardware platforms may be used asthe hardware platform(s) for one or more of the elements describedherein. A computer with user interface elements may be used to implementa personal computer (PC) or any other type of work station or terminaldevice. A computer may also act as a server if appropriately programmed.

FIGS. 4A and 4B are block diagrams illustrating exemplary processingdevices 140A and 140B according to some embodiments of the presentdisclosure. The processing devices 140A and 140B may be exemplaryprocessing devices 140B as described in connection with FIG. 1 . In someembodiments, the processing device 140A may be configured to processinformation and/or data to determine a set of training samples. Theprocessing device 140A may be further configured to generate an ROIdetection model using the set of training samples. The processing device140B may be configured to identify one or more ROI(s) in a target imageby applying the ROI detection model to the target image. In someembodiments, the processing devices 140A and 140B may be respectivelyimplemented on a processing unit (e.g., a processor 210 illustrated inFIG. 2 or a CPU 340 as illustrated in FIG. 3 ). Merely by way ofexample, the processing devices 140A may be implemented on a computingdevice 200, and the processing device 140B may be implemented on a CPU340 of a terminal device. Alternatively, the processing devices 140A and140B may be implemented on a same computing device 200 or a same CPU340. For example, the processing devices 140A and 1406 may beimplemented on a same computing device 200.

As shown in FIG. 4A, the processing device 140A may include anacquisition module 410, a training sample generation module 415, and amodel generation module 420.

The acquisition module 410 may be configured to acquire informationrelating to the training of the ROI detection model, such as a pluralityof training samples and/or a plurality of training images. In someembodiments, the acquisition module 410 may acquire a plurality oftraining images. Each of the plurality of training images may beannotated with one or more ROIs. The training image may refer to animage of a sample object that has one or more known ROIs (which areannotated in the training image). The ROI(s) in the training image maybe annotated in any suitable manner (e.g., by assigning a marker or alabel to each pixel of the training image, or by marking a ground truthbounding box). More descriptions regarding the training image and theROI(s) may be found elsewhere in the present disclosure. See, e.g.,operation 502 and relevant descriptions thereof.

The training sample generation module 415 may be configured to determinea plurality of training samples for training the ROI detection modelbased at least in part on the plurality of training images. For example,the ROI detection model may be generated by training a cascaded neuralnetwork that includes a plurality of models. The plurality of models mayinclude a first model and at least one second model downstream to thefirst model in the cascaded neural network. The training samplegeneration module 415 may be configured to determine a plurality oftraining samples for the first model and a plurality of training samplesfor each of the second model. More descriptions regarding the generationof the training samples may be found elsewhere in the presentdisclosure. See, e.g., FIGS. 6A and 6B and relevant descriptionsthereof.

The model generation module 420 may be configured to generate the ROIdetection model based on the training samples. For example, the modelgeneration may train a cascaded neural network using the plurality oftraining images. The cascaded neural network may include a plurality ofsequentially connected models. In some embodiments, at least one modelof the cascaded neural network may include a multi-scale modelconfigured to perform ROI detection at a plurality of resolution levels.In some embodiments, the plurality of sequentially connected models maybe sequentially trained in the training of the cascaded neural network.More descriptions regarding the generation of the ROI detection modelmay be found elsewhere in the present disclosure. See, e.g., operation504 and FIG. 7 and relevant descriptions thereof.

As shown in FIG. 4B, the processing device 140B may include anacquisition module 430 and an ROI detection module 440.

The acquisition module 430 may be configured to acquire informationrelating to the application of the ROI detection model. For example, theacquisition module 430 may acquire a target image whose ROI is to bedetected and the ROI detection model. More descriptions regardingacquisition of the target image and the ROI detection model may be foundelsewhere in the present disclosure. See, e.g., operation 802 andrelevant descriptions thereof.

The ROI detection module 440 may be configured to perform ROI detectionon the target image by applying the ROI detection model to the targetimage. In some embodiments, a plurality of trained models of the ROIdetection model may be configured to perform ROI detection on the targetimage independently in a parallel manner or sequentially in a serialmanner. In some embodiments, the ROI detection result may include one ormore detected ROIs in the target image. The ROI detection result may beoutputted by the ROI detection model directly. Alternatively, the ROIdetection result may be determined by the ROI detection module 440 basedon an output of the ROI detection model. More descriptions regardingperforming ROI detection on the target may be found elsewhere in thepresent disclosure. See, e.g., operation 804 and relevant descriptionsthereof.

It should be noted that the above description is merely provided for thepurposes of illustration, and not intended to limit the scope of thepresent disclosure. For persons having ordinary skills in the art,multiple variations and modifications may be made under the teachings ofthe present disclosure. However, those variations and modifications donot depart from the scope of the present disclosure. In someembodiments, the processing device 140A and/or the processing device1406 may share two or more of the modules, and any one of the modulesmay be divided into two or more units. For instance, the processingdevices 140A and 1406 may share a same acquisition module; that is, theacquisition module 410 and the acquisition module 430 are a same module.In some embodiments, the processing device 140A and/or the processingdevice 140B may include one or more additional modules, such a storagemodule (not shown) for storing data. In some embodiments, the processingdevice 140A and the processing device 140B may be integrated into oneprocessing device 140. In some embodiments, the determination of the setof training samples may be performed by a processing device, while thegeneration of the ROI detection model using the set of training samplesmay be performed by another processing device.

FIG. 5 is a flowchart illustrating an exemplary process for generatingan ROI detection model according to some embodiments of the presentdisclosure. In some embodiments, process 500 may be executed by theimaging system 100. For example, the process 500 may be implemented as aset of instructions (e.g., an application) stored in a storage device(e.g., the storage device 150, the storage 220, and/or the storage 390).In some embodiments, the processing device 140A (e.g., the processor 210of the computing device 200, the CPU 340 of the mobile device 300,and/or one or more modules illustrated in FIG. 4A) may execute the setof instructions and may accordingly be directed to perform the process500.

The ROI detection model may be a neural network model that is configuredto receive a target image as an input, and output one or more ROIsand/or data related to the one or more ROIs in the target image. In someembodiments, the target image may be an image of an object. The objectmay include any organic or inorganic mass, such as a biological objectand/or a non-biological object. As used herein, an ROI of the targetimage may refer to a portion in the target image that represents aphysical region of interest of the object. For example, the target imagemay be an image of a patient, and the ROI of the target image may be alesion area, a specific organ, a specific tissue, specific cell(s), or awhole body of the patient.

In some embodiments, the ROI may include a lesion of the object. The ROIdetection model may be a lesion detection model configured to perform alesion detection on the target image. A lesion may refer to a damage (orpotential damage) and/or an abnormal change (or potential change) in thetissue of the object, usually caused by disease or trauma. Exemplarylesions may include a soft-tissue lesion, a diabetes-associated lesion,a bone lesion, a brain lesion, a skin lesion, a gastrointestinal lesion,an endodermal lesion, or the like, or any combination thereof.

In 502, the processing device 140A (e.g., the acquisition module 410,the processing circuits of the processor 210) may acquire a plurality oftraining images. Each training image may be annotated with one or moreROIs.

A training image may refer to an image of a sample object that has oneor more known ROIs (which are annotated in the training image). In someembodiments, the sample object may be of the same type of object as theobject in the target image. The ROI(s) in the training image maycorrespond to the same type of physical portion as the ROI(s) in thetarget image to be detected. For example, if the ROI detection model isused to detect a specific lesion (e.g., a prostatic cancer) on a targetimage of a patient, the training image may be an image of a samplepatient, wherein one or more lesion areas representing the specificlesion of the sample patient are annotated in the image. As anotherexample, if the ROI detection model is used to segment a specific organfrom a target image of a patient, the training image may be an image ofa sample patient, wherein the specific organ of the sample patient isannotated in the image. In some embodiments, a set of images may beannotated with different types of ROIs to generate different sets oftraining images, wherein the different sets of training images may beused to train different types of ROI detection models. For example, aset of chest CT images may be annotated with the heart to generate a setof training images used to train a heart detection model, and the set ofchest CT images may be annotated with the lung to generate another setof training images used to train a lung detection model. In someembodiments, different sets of images may be annotated with differenttypes of ROIs to generate different sets of training images, wherein thedifferent sets of training images may be used to train different typesof ROI detection models.

In some embodiments, the training image may be a one-dimensional image,a 2D image (e.g., a slice image), a 3D image, a 4D image, and/or anyrelated image data (e.g., scan data, projection data), or the like. Thetraining image may be stored in any image format, for example, a BMPformat, a JPEG format, a TIFF format, a PNG format, a DICOM format, aVTK format, or the like. In some embodiments, the training image mayinclude a plurality of elements, each of which may have a propertyvalue. For example, the training image may be a 2D image including aplurality of pixels, and each pixel may have a pixel value. As anotherexample, the training image may be a 3D image including a plurality ofvoxels, and each voxel may have a voxel value. For the convenience ofdescription, the term “pixel” and “voxel” in the present disclosure areused interchangeably to refer to an element of an image. In someembodiments, the training image may be generated using a biomedicalimaging technique as described elsewhere in this disclosure. Forexample, the training image may be a CT image, an MRI image, an X-rayimage, a PET image, an OCT image, a US image, an IVUS image, a NIRSimage, etc. In some embodiments, the training image and the target imagemay be generated using the same biomedical imaging technique. Forexample, a plurality of CT images may be used as training images forgenerating an ROI detection model that is used to detect one or moreROIs in a target CT image.

In some embodiments, the ROI(s) of a training image may be annotatedautomatically, semi-automatically, or manually. In an automaticannotation approach, the ROI(s) of the training image may be annotatedautomatically by a computing device (e.g., the computing device 200 asillustrated in FIG. 2 ) based on an image analysis technique withoutuser intervention. In a semi-automatic annotation approach, the ROI(s)of the training image may be annotated by a computing device (e.g., thecomputing device 200 as illustrated in FIG. 2 ) with user intervention.Exemplary user intervention may include providing information regardinga specific algorithm (e.g., a segmentation algorithm) to be used in ROIsegmentation and/or annotation, a parameter (e.g., a location parameter)related to a region to be annotated, or the like, or a combinationthereof. For instance, during a semi-automatic annotation, a userprovides information identifying a characteristic feature (e.g., bymarking it on an image to be annotated on a user interface displayingthe image), and a computing device performs the ROI annotation based onthe information in combination with a segmentation algorithm and/orparameter. In a manual annotation approach, the ROI(s) of the trainingimage may be annotated by a user (e.g., a doctor) via a terminal device(e.g., the terminal 130). In some embodiments, the ROI(s) of differenttraining images may be annotated by the same annotation approach ordifferent annotation approaches.

In some embodiments, an ROI of a training image may be annotated in anysuitable manner. For example, the ROI of the training image may beannotated by assigning a marker or a label to each pixel of the trainingimage. The marker or the label assigned to the pixel may represent, forexample, whether the pixel belongs to an ROI of the training image ornot, a possibility that the pixel belongs to an ROI of the trainingimage, etc. Merely by way of example, each pixel of the training imagemay be assigned with “0” or “1,” wherein “0” represents that a pixelbelongs to a non-ROI of the training image and “1” represents that apixel belongs to an ROI of the training image. Optionally, the trainingimage may be presented based on the maker or label assigned to eachpixel of the training image. For example, the training image may bepresented as a binary image, wherein one or more pixels assigned with“0” may be white and one or more pixels assigned with “1” may be blackin the binary image. In such cases, in the training image, a white areamay represent a non-ROI and a black area may represent an ROI.

Alternatively, the ROI of the training image may be annotated by aground truth bounding box. The ground truth bounding box may refer to abounding box enclosing a known ROI (e.g., an ROI annotated by a user) inthe training image. The ground truth bounding box may have any shape andsize. For example, the ground truth bounding box may have the shape of asquare, a rectangle, a triangle, a polygon, a circle, an ellipse, anirregular shape, or the like. In some embodiments, the ground truthbounding box may be a minimum bounding box that has a preset shape(e.g., a rectangle, a square, a polygon, a circle, an ellipse) andencloses the ROI of the training image.

In some embodiments, the training images may be obtained by theprocessing device 140A from a storage device (e.g., the storage device150, the storage 220, and/or the storage 390) of the imaging system 100via a network (e.g., the network 120). For example, the training imagesmay include a plurality of historical images generated using the imagingdevice 110, wherein the historical images have been annotated with oneor more lesion areas by a doctor in diagnosis. The historical images maybe stored in the storage device of the imaging system 100 and retrievedby the processing device 140A from the storage device. Additionally oralternatively, the training images may be obtained by the processingdevice 140A from an external source (e.g., a medical database) via anetwork (e.g., the network 120).

In 504, the processing device 140A (e.g., the model generation module420, the processing circuits of the processor 210) may generate the ROIdetection model by training a cascaded neural network using the trainingimages.

The cascaded neural network may include a plurality of sequentiallyconnected models. The plurality of models include a first model and atleast one second model downstream to the first model in the cascadedneural network. For example, the cascaded neural network may be acascaded neural network A including N models (i.e., a 1^(st) model, a2^(nd) model, . . . , and a N^(th) model), wherein the 1^(st) model maybe connected to the 2^(nd) model, the 2^(nd) model may be connected tothe 3^(rd) model, . . . , and the (N−1)^(th) model may be connected tothe N^(th) model. In some embodiments, a model of the cascaded neuralnetwork may be a convolutional neural network (CNN) model, a fasterregion-based convolutional neural network (FASTER RCNN), a regionproposal network (RPN), a classification network (e.g., a VisualGeometry Group (VGG) network, an Alex Krizhevsky (AlexNet), a ResNet(residual neural network)), a multi-scale model, or any other suitabletype of model. The plurality of models of the cascaded neural networkmay be of the same type of model or different types of models. In someembodiments, at least one model of the cascaded neural network may be amulti-scale model configured to perform ROI detection at a plurality ofresolution levels (or image scales). For example, the multi-scale modelmay have the same or similar structure as a multi-scale model 1200 asshown in FIG. 12 .

In some embodiments, the models may be sequentially trained in thetraining of the cascaded neural network using different trainingsamples. Taking the cascaded neural network A as an instance, the 1^(st)model, the 2^(nd) model, the 3^(rd) model, . . . , and the N^(th) modelmay be trained in sequence. For each model, the processing device 140Amay determine a plurality of training samples of the model based atleast in part on the training images, and train the model using thecorresponding training samples. In some embodiments, the trainingsamples of the first model may be determined based on the trainingimages by, for example, performing one or more operations of process600A in FIG. 6A. The training samples of each of the at least one secondmodel may be determined based on the training images and one or moretrained models generated before the training of the second model. Theone or more trained models generated before the training of a specificsecond model may refer to a previously trained model connected to thespecific second model or one or more of all the trained model(s)generated before the training of the specific second model. For example,the one or more trained models before the training of the i^(th) modelof the cascaded neural network A may refer to the (i−1)^(th) trainedmodel or one or more of all the 1^(st) trained model, the 2^(nd) trainedmodel, . . . , and the (i−1)^(th) trained model that are generatedbefore the training of the i^(th) model. In some embodiments, theprocessing device 140A may perform one or more operations of process600B in FIG. 6B to determine the training samples of the second model.In some embodiments, the training of a model of the cascaded neuralnetwork may include one or more iterations. For example, the processingdevice 140A may perform one or more iterations of process 700 asdescribed in connection with FIG. 7 to train a model of the cascadedneural network.

It should be noted that the above description regarding the process 500is merely provided for the purposes of illustration, and not intended tolimit the scope of the present disclosure. For persons having ordinaryskills in the art, multiple variations or modifications may be madeunder the teachings of the present disclosure. However, those variationsand modifications do not depart from the scope of the presentdisclosure. In some embodiments, one or more operations may be added oromitted. For example, in operation 504, the processing device 140A maypreprocess the training images, and generate the ROI detection modelbased on the preprocessed training images. The preprocessing of thetraining images may include, for example, an image frittering, an imagenormalization, an image denoising, or the like, or any combinationthereof. For example, the processing device 140A may normalize the pixelvalues of a plurality of pixels in the training images to a specificrange (e.g., 0-255) based on a window width and/or a window level of thepixels. In some embodiments, after the ROI detection model is generated,the processing device 140A may further test the ROI detection modelusing a set of testing images. Additionally or alternatively, theprocessing device 140A may update the ROI detection model periodicallyor irregularly based on one or more newly-generated training images(e.g., new annotated images generated in medical diagnosis).

FIG. 6A is a flowchart illustrating an exemplary process for determininga plurality of training samples of a first model of a cascaded neuralnetwork according to some embodiments of the present disclosure. In someembodiments, process 600A may be executed by the imaging system 100. Forexample, the process 600A may be implemented as a set of instructions(e.g., an application) stored in a storage device (e.g., the storagedevice 150, the storage 220, and/or the storage 390). In someembodiments, the processing device 140A (e.g., the processor 210 of thecomputing device 200, the CPU 340 of the mobile device 300, and/or oneor more modules illustrated in FIG. 4A) may execute the set ofinstructions and may accordingly be directed to perform the process600A. In some embodiments, one or more operations of the process 600Amay be performed to achieve at least part of operation 504 as describedin connection with FIG. 5 .

In 602, the processing device 140A (e.g., the training sample generationmodule 415, the processing circuits of the processor 210) may determinea plurality of first negative samples of the first model and a pluralityof positive samples based on the plurality of training images. As usedherein, a first negative sample may refer to a negative sample to beused for training the first model. Each first negative sample may beindicative of at least a portion of a non-ROI in the training images.Each of the positive samples may be indicative of at least a portion ofan ROI in the training images.

In some embodiments, a sample (e.g., a first negative sample, a positivesample) may be a pixel. For example, the processing device 140A maydesignate a pixel in an ROI of a training image as a positive sample,and designate a pixel outside the ROI(s) of a training image as a firstnegative sample. In some embodiments, as described in operation 502,each pixel in the training images may be assigned with a marker or alabel (e.g., “0” or “1”) to indicate whether the pixel belongs to an ROIor not. In such a case, the processing device 140A may determine thefirst negative samples and the positive samples based on the markers orthe labels of the pixels of the training images. For example, a pixel isassigned with “1” and a pixel assigned with “0” may be regarded as apositive pixel in an ROI and a negative pixel in a non-ROI of thetraining images, respectively. The processing device 140A may designateall or a portion of the positive pixels of the training images as thepositive samples, and designate all or a portion of the negative pixelsof the training images as the first negative samples.

In some embodiments, a sample (e.g., a first negative sample, a positivesample) may be an anchor box. As used herein, an anchor box may refer toa template bounding box that encloses a pixel in a training image andrepresents a candidate ROI enclosing the pixel. An anchor box may have apreset shape (e.g., a square, a rectangle, a triangle, a polygon, acircle, an irregular shape) and/or a preset size (e.g., 5 mm×5 mm, 5mm×10 mm, 10 mm×10 mm). In some embodiments, for each of a plurality ofpixels in the training images, the processing device 140A may define oneor more anchor boxes enclosing the pixel to represent one or morecandidate ROIs enclosing the pixel. Optionally, each pixel may belocated at a center of each corresponding anchor box defined for thepixel. In some embodiments, a plurality of anchor boxes may be definedfor each pixel of the training images, wherein the anchor boxes may havedifferent shapes and/or sizes to represent different candidate ROIsenclosing the pixel. For example, for a training image including 512×512pixels, the processing device 140A may define nine anchor boxes for eachpixel of the training image, thereby generating 512×512×9 anchor boxes.The nine anchor boxes of each pixel may have different shapes and/ordifferent sizes. Merely by way of example, the nine anchor boxes may berectangles having different sizes.

After the anchor boxes are defined, the processing device 140A maycompare the anchor boxes with the ROIs of the training images togenerate a comparison result. For example, in some embodiments, the ROIsof the training images may be annotated using a plurality of groundtruth bounding boxes as described in operation 502. For each anchor boxin each training image, the processing device 140A may determine anintersection over union (IOU) between the anchor box and each groundtruth bounding box. The processing device 140A may further determine thefirst negative samples and the positive samples among the anchor boxesbased on the comparison result. For example, for an anchor box in atraining image, if an IOU between the anchor box and a specific groundtruth bounding box in the training image is greater than an IOUthreshold (e.g., 0.5, 0.8, or 0.9), the anchor box may be regarded as apositive anchor box corresponding to the ground truth bounding box. Ifan IOU between the anchor box and each ground truth bounding box in thetraining image is smaller than the IOU threshold, the anchor box may beregarded as a negative anchor box. For each anchor box in each trainingimage, the processing device 140A may determine whether the anchor boxis a positive anchor box or a negative anchor box. Further, theprocessing device 140A may designate all or a portion of the positiveanchor boxes of the training images as the positive samples, anddesignate all or a portion of the negative anchor boxes of the trainingimages as the first negative samples.

In some embodiments, a ratio of a count of the positive samples to acount of the first negative samples may be equal to or greater than athreshold ratio. The threshold ratio may be equal to any suitable value,for example, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, etc. For example,the threshold ratio may be equal or close to 0.2. In some cases, anumber (or count) of the positive pixels (or positive anchor boxes) maybe much smaller than a number (or count) of the negative pixels (ornegative anchor boxes). For example, a ratio of a count of positivepixels in lesion areas of a plurality of training images to a count ofnegative pixels outside the lesion areas of the training images may beequal to or smaller than 1:10⁶. Training the first model directly usingall the positive pixels (or positive anchor boxes) and the negativepixels (or negative anchor boxes) of the training images may generate atrained first model having low accuracy. Therefore, it is desirable thatthe processing device 140A determines the first negative samples and thepositive samples based on the positive pixels (or positive anchor boxes)and the negative pixels (or negative anchor boxes) so that the ratioreaches a desirable value. For example, the processing device 140A mayselect a part of the negative pixels (or negative anchor boxes) of thetraining images as the first negative samples of the first model, andselect all of the positive pixels (or positive anchor boxes) as thepositive samples, wherein a ratio of a count of the selected positivesamples to a count of the selected negative samples may be equal to orgreater than 0.2.

In 604, the processing device 140A (e.g., the training sample generationmodule 415, the processing circuits of the processor 210) may designatethe first negative samples and the positive samples as the trainingsamples of the first model.

It should be noted that the above description regarding the process 600Ais merely provided for the purposes of illustration, and not intended tolimit the scope of the present disclosure. For persons having ordinaryskills in the art, multiple variations or modifications may be madeunder the teachings of the present disclosure. However, those variationsand modifications do not depart from the scope of the presentdisclosure. In some embodiments, one or more operations may be added oromitted. For example, the processing device 140A may update the trainingsamples of the first model periodically or irregularly based on one ormore newly-generated training images (e.g., new annotated imagesgenerated in medical diagnosis). In some embodiments, the positivepixels (or positive anchor boxes) and the negative pixels (or negativeanchor boxes) may be previously determined for the training images andstored in a storage device. The processing device 140A may obtain thedetermination result from the storage device, and determine the trainingsamples of the first model based on the determination result.

In some embodiments, the processing device 140A may determine a groundtruth classification map based on the training samples of the firstmodel. The ground truth classification map may include a ground truthclassification of each training sample of the first model regardingwhether the training sample is a positive sample or a negative sample.For example, in the ground truth classification map, a positive sample(e.g., a positive pixel or a positive anchor box) may be labeled with“1” and a negative sample (e.g., a negative pixel or a negative anchorbox) of the first model may be labeled with “0.”

In some embodiments, the training samples of the first model may includea plurality of anchor boxes. The processing device 140A may determinethe ground truth classification map as well as a ground truth regressionmap. The ground truth regression map may include one or more groundtruth location parameters of at least one of the anchor boxes. In someembodiments, the ground truth regression map may include one or moreground truth location parameters of each positive anchor box. The groundtruth location parameter(s) of a positive anchor box may indicate aground truth position or a ground truth size of the positive anchor boxrelative to a corresponding ground truth bounding box. Merely by way ofexample, the positive anchor box and the corresponding ground truthbounding box may be boxes in a 3D space (e.g., a space defined by anX-axis, a Y axis, and a Z axis). The ground truth location parameter(s)of the positive anchor box may include one or more of Δx, Δy, Δz,Δs_(x), Δs_(y), and Δs_(z). Δx, Δy and Δz may refer to distances betweena center point of the positive anchor box and a center point of thecorresponding ground truth bounding box along the X-axis, the Y-axis,and the Z-axis, respectively. Δs_(x), Δs_(y), and Δs_(z) may refer to alength difference along the X-axis, a width difference along the Y-axis,and a height difference along the Z-axis between the positive anchor boxand the corresponding ground truth bounding box. As another example, thepositive anchor box and the corresponding ground truth bounding box maybe boxes in a 2D space (e.g., a space defined by the X-axis and the Yaxis). The ground truth location parameter(s) of the positive anchor boxmay include one or more of Δx, Δy, Δs_(x), and Δs_(y).

In some embodiments, the ground truth classification map and/or theground truth regression map may be used to train a model (e.g., thefirst model, a second model) of the cascaded neural network. Moredescriptions regarding the use of the ground truth classification mapand/or the ground truth regression map in model training may be foundelsewhere in the present disclosure. See, e.g., FIG. 7 and relevantdescriptions thereof.

FIG. 6B is a flowchart illustrating an exemplary process for determininga plurality of training samples of a second model of a cascaded neuralnetwork according to some embodiments of the present disclosure. In someembodiments, process 600B may be executed by the imaging system 100. Forexample, the process 600B may be implemented as a set of instructions(e.g., an application) stored in a storage device (e.g., the storagedevice 150, the storage 220, and/or the storage 390). In someembodiments, the processing device 140A (e.g., the processor 210 of thecomputing device 200, the CPU 340 of the mobile device 300, and/or oneor more modules illustrated in FIG. 4A) may execute the set ofinstructions and may accordingly be directed to perform the process600B.

In some embodiments, one or more operations of the process 600B may beperformed to achieve at least part of operation 504 as described inconnection with FIG. 5 . In some embodiments, the cascaded neuralnetwork may include a plurality of sequentially connected second models.The process 600B may be sequentially performed for each second model.For illustration purposes, an implementation of the process 600B for asecond model is described hereinafter.

In 606, the processing device 140A (e.g., the training sample generationmodule 415, the processing circuits of the processor 210) may determinea plurality of predicted positive samples by applying the one or moretrained models generated before the training of the second model to thetraining images. The predicted positive samples may represent aplurality of predicted ROIs in the training images.

As described in connection with 604, the one or more trained model(s)generated before the training of the second model may include apreviously trained model connected to the second model or one or more ofall the trained model(s) generated before the training of the secondmodel. For example, the one or more trained models before the trainingof the i^(th) model of the cascaded neural network A may refer to the(i−1)^(th) trained model or one or more of all the 1^(st) trained model,the 2^(nd) trained model, . . . , and the (i−1)^(th) trained model thatare generated before the training of the i^(th) model. The processingdevice 140A may apply the trained model(s) to the training images togenerate an output of the trained model(s). The processing device 140Amay further determine the predicted positive samples based on the outputof the trained model(s).

In some embodiments, the training samples of the first model may includea plurality of pixels of the training images. The processing device 140Amay determine a plurality of predicted positive pixels based on theoutput of the trained model(s), and designate the predicted positivepixels as the predicted positive samples. Alternatively, the trainingsamples of the first model may include a plurality of anchor boxes ofthe training images. The processing device 140A may determine aplurality of predicted positive anchor boxes based on the output of thetrained model(s), and designate the predicted positive anchor boxes asthe predicted positive samples. More descriptions regarding thedetermination of the predicted positive pixels and/or the predictedpositive anchor boxes may be found elsewhere in the present disclosure.See, e.g., operation 704 in FIG. 7 and relevant descriptions thereof.

In 608, the processing device 140A (e.g., the training sample generationmodule 415, the processing circuits of the processor 210) may identify,among the predicted positive samples, one or more false positivesamples.

As used herein, a false positive sample may refer to a negative sample(e.g., a negative pixel, a negative anchor box) that is determined as apredicted positive sample by one or more trained models. In someembodiments, the processing device 140A may compare the predictedpositive samples with the true positive samples (which is described inoperation 602). If a predicted positive sample is not a true positivesample, the predicted positive sample may be designated as a falsepositive sample. For example, the false positive sample(s) may include apredicted positive pixel which is actually a negative pixel and/or apredicted positive anchor box which is actually a negative anchor box.In some embodiments, the predicted positive samples are the predictedpositive anchor boxes, the processing device 140A may compare thepredicted positive anchor boxes with the ground truth bounding boxes. Ifan IOU between a predicted positive anchor box and each ground truthbounding box is smaller than an IOU threshold, the predicted positiveanchor box may be designated as a false positive sample.

In some embodiments, the processing device 140A may determine a falsepositive rate of the trained model(s) generated before the training ofthe second model to measure accuracy of the trained model(s). The falsepositive rate of the trained model(s) may be assessed based on the ratioof a count of the determined false positive sample(s) to a count of thepositive samples (e.g., a count of the true positive samples, a count ofthe true positive samples plus the false positive samples).

In 610, the processing device 140A (e.g., the training sample generationmodule 415, the processing circuits of the processor 210) may determinea plurality of second negative samples of the second model. The secondnegative samples may include at least a portion of the one or more falsepositive samples. As used herein, a second negative sample may refer toa negative sample to be used for training the second model.

In some embodiments, the second negative samples may include all or aportion of the false positive sample(s). Additionally or alternatively,the second negative samples may also include one or more negative pixelsor one or more negative anchor boxes. As described in FIG. 6A, a portionof the negative pixels or negative anchor boxes of the training imagesmay be selected as the first negative samples of the first model. Thesecond negative samples may include all or a portion of the remainingnegative pixels or negative anchor boxes of the training images that arenot included in the first negative samples. In some embodiments, a ratioof a count of the second positive samples to a count of the negativesamples may be equal to or greater than a threshold ratio (e.g., 0.15,0.2, 0.25).

In 612, the processing device 140A (e.g., the training sample generationmodule 415, the processing circuits of the processor 210) may designatethe second negative samples and the positive samples as the trainingsamples of the current second model. The positive samples of the currentsecond model may include all or a portion of the positive samples usedto train the first model or one or more second models already trainedprior to the training of the current second model. For instance, thepositive samples of the current second model may include all thepositive samples used to train the first model or one or more secondmodels already trained prior to the training of the current secondmodel.

According to some embodiments of the present disclosure, the trainingsamples of the second model may include one or more false positivesamples predicted by the trained model(s) generated before the trainingof the second model. The second model may be trained to learn one ormore features of the false positive sample(s), thus being more reliablein distinguishing a non-ROI from an ROI than the tainted model(s)generated before the training of the second model. This may furtherimprove the accuracy and performance of the ROI detection model to begenerated.

It should be noted that the above description regarding the process 600Bis merely provided for the purposes of illustration, and not intended tolimit the scope of the present disclosure. For persons having ordinaryskills in the art, multiple variations or modifications may be madeunder the teachings of the present disclosure. However, those variationsand modifications do not depart from the scope of the presentdisclosure. In some embodiments, one or more operations may be added oromitted. For example, the processing device 140A may update the trainingsamples of the second mode periodically or irregularly based on one ormore newly-generated training images (e.g., new annotated imagesgenerated in medical diagnosis).

FIG. 7 is a flowchart illustrating an exemplary process for generating atrained model by training a model using a plurality of training samplesof the model according to some embodiments of the present disclosure. Insome embodiments, process 700 may be executed by the imaging system 100.For example, the process 700 may be implemented as a set of instructions(e.g., an application) stored in a storage device (e.g., the storagedevice 150, the storage 220, the storage 390). In some embodiments, theprocessing device 140A (e.g., the processor 210 of the computing device200, the CPU 340 of the mobile device 300, and/or one or more modulesillustrated in FIG. 4A) may execute the set of instructions and mayaccordingly be directed to perform the process 700.

In some embodiments, one or more operations of the process 700 may beperformed to achieve at least part of operation 504 as described inconnection with FIG. 5 . In some embodiments, the cascaded neuralnetwork may include a plurality of sequentially connected modelsincluding a first model and at least one second model downstream to thefirst model. The process 700 may be sequentially performed for the eachmodel of the cascaded neural network. For illustration purposes, animplementation of the process 700 for a model of the cascaded neuralnetwork is described hereinafter.

In some embodiments, the model to be trained may have one or more modelparameters. Exemplary model parameters may include the number (or count)of layers, the number (or count) of nodes, a loss function, or the like,or any combination thereof. Before the training, the model may have oneor more initial parameter values of the model parameter(s). In thetraining of the model, one or more parameter values of the model may beupdated. In some embodiments, the training of the model may include oneor more iterations. For illustration purposes, a current iteration ofthe iteration(s) is described in the following description. The currentiteration may include one or more operations of the process 700.

In 702, the processing device 140A (e.g., the model generation module420, the processing circuits of the processor 210) may obtain an outputof the model in the current iteration by applying the model in thecurrent iteration to the plurality of training samples of the model.

In some embodiments, the training samples of the model may include aplurality of pixels as described elsewhere in this disclosure (e.g.,FIGS. 6A and 6B, and the relevant descriptions). The output of the modelmay include a first probability map. The first probability map mayinclude a plurality of first probability values of the pixels, eachfirst probability value being indicative of a predicted probability thata corresponding pixel belongs to an ROI.

In some embodiments, the training samples of the model may include aplurality of anchor boxes as described elsewhere in this disclosure(e.g., FIGS. 6A and 6B, and the relevant descriptions). Each anchor boxmay enclose a pixel in the training images and represent a candidate ROIenclosing the pixel. The output of the model may include a secondprobability map and a regression map. The second probability map mayinclude a plurality of second probability values of the anchor boxes,each second probability value being indicative of a predictedprobability that a corresponding anchor box belongs to an ROI. Theregression map may include one or more predicted location parameters ofone or more of the anchor boxes, each predicted location parameter beingindicative of a predicted position of a corresponding anchor boxrelative to an ROI, a predicted size of the corresponding anchor boxrelative to an ROI, or the like, or a combination thereof. The predictedlocation parameter(s) of an anchor box may include one or more similarparameters as the ground truth location parameter(s) of a positiveanchor box as described in connection with FIG. 6A. In some embodiments,the regression map may include one or more predicted location parametersof each of the anchor boxes. Alternatively, the regression map mayinclude one or more predicted location parameters of a portion of theanchor boxes, such as the positive anchor boxes determined in 602.

In 704, the processing device 140A (e.g., the model generation module420, the processing circuits of the processor 210) may determine a valueof a loss function based on the training samples and the output of themodel.

As used herein, a loss function may refer to a function that measures adifference between the output of the model and the actual value, whereinthe difference may indicate the accuracy of the model. In someembodiments, the training samples of the model may include a pluralityof pixels, and the output of the model may include the first probabilitymap as described in connection with 702. The loss function may be afirst classification loss configured to measure the accuracy of themodel in classifying the pixels. In some embodiments, the processingdevice 140A may determine a first predicted classification map includinga predicted classification of each pixel based on the first probabilityvalue of the pixel. The first predicted classification of each pixel mayindicate whether the pixel is predicted to belong to an ROI or not. Forexample, if a pixel in the training sample has a first probability valuegreater than a threshold value T₁, the pixel may be classified as apredicted positive pixel which is predicted to be within an ROI of atraining image. If a pixel in the training sample has a firstprobability value smaller than the threshold value T₁, the pixel may beclassified as a predicted negative pixel which is predicted to be withina non-ROI of a training image. The processing device 140A may determinethe first classification loss by comparing the first predictedclassification map and the ground truth classification map (as describedin FIG. 6A). The first classification loss may be, for example, a logloss function, a cross-entropy loss function.

In some embodiments, the threshold value T₁ may be a default setting ofthe imaging system 100 or be determined by the processing device 140Aaccording to the first probability map outputted in the currentiteration. In some embodiments, the processing device 140A may determinethe threshold value T₁, wherein the determined threshold value T₁ may besuch that all or at least a certain portion (e.g., 99%, 95%) of thepositive samples are determined as predicted positive samples identifiedusing the model, as trained, according to the determined threshold valueT₁. For example, the determined threshold value T₁ may be smaller thanthe smallest first probability value of the positive pixels in thepixels, such that each positive pixel in the pixels may be determined asa predicted positive pixel.

In some embodiments, the training samples of the model may include aplurality of anchor boxes, and the output of the model may include thesecond probability map and the regression map as described in connectionwith 702. The loss function may include a second classification lossassociated with the second probability map and a regression lossassociated with the regression map. The second classification loss maybe used to measure the accuracy of the model in classifying the anchorboxes. In some embodiments, the processing device 140A may determine asecond predicted classification map including a predicted classificationof each anchor box based on the second probability value of the anchorbox. For example, if an anchor box in the training sample has a secondprobability value greater than a threshold value T₂, the anchor box maybe classified as a predicted positive anchor box. If an anchor box inthe training sample has a second probability value smaller than thethreshold value T₂, the anchor box may be classified as a predictednegative anchor box. The processing device 140A may determine the secondclassification loss by comparing the second predicted classification mapand the ground truth classification map. The second classification lossmay be, for example, a log loss function, a cross-entropy loss function,etc. The regression loss may be configured to measure the accuracy ofthe model in determining location parameters of the anchor boxes. Theprocessing device 140A may determine the regression loss by comparingthe regression map with the ground truth regression map (as described inFIG. 6A). The regression loss may be, for example, an L1 norm function,an L2 norm function, etc. In some embodiments, the value of the lossfunction may be determined based on the value of the secondclassification loss alone, the value of the regression loss alone, or acombination thereof. For instance, the value of the loss function may beequal to the value of the second classification loss, or the value ofthe regression loss, or a sum (or weighted sum) of the values of thesecond classification loss and the regression loss. In some embodiments,similar to the threshold value T₁, the threshold value T₂ may be adefault setting of the imaging system 100 or be determined by theprocessing device 140A according to the second probability map. Forexample, the threshold value T₂ may be determined in a similar manner asthe threshold value T₁, and the descriptions thereof are not repeatedhere.

In 706, the processing device 140A (e.g., the model generation module420, the processing circuits of the processor 210) may determine whethera first termination condition is satisfied in the current iterationbased on the value of the loss function.

An exemplary first termination condition may be that the value of theloss function obtained in the current iteration is less than a thresholdvalue. Other exemplary first termination conditions may include that acertain count of iterations have been performed, that the loss functionconverges such that the difference of the values of the loss functionobtained in a previous iteration and the current iteration is within athreshold value, etc.

In 708, upon a determination that the first termination condition issatisfied in the current iteration, the processing device 140A (e.g.,the model generation module 420, the processing circuits of theprocessor 210) may proceed to operation 710. In 710, the processingdevice 140A (e.g., the model generation module 420, the processingcircuits of the processor 210) may designate the model in the currentiteration as the trained model.

Upon a determination that the first termination condition is notsatisfied in the current iteration, the processing device 140A mayproceed to operation 712. In 712, the processing device 140A (e.g., themodel generation module 420, the processing circuits of the processor210) may update the model. For example, the processing device 140A mayupdate the value(s) of the model parameter(s) of the model based on thevalue of the loss function according to, for example, a backpropagationalgorithm.

In 712, the processing device 140A (e.g., the model generation module420, the processing circuits of the processor 210) may designate theupdated model in the current iteration as a model in a next iteration.

After 712, the processing device 140A may proceed to operation 702 toperform the next iteration until the first termination condition issatisfied. After the first termination condition is satisfied in acertain iteration, the model in the certain iteration having the updatedvalue(s) of the model parameter(s) may be designated as the trainedmodel.

In some embodiments, the model may be a second model of the cascadedneural network. After the trained second model is generated, theprocessing device 140A may further determine whether a secondtermination condition is satisfied to determine whether the training ofthe cascaded neural network is finished. Taking the M^(th) model of thecascaded neural network A as an instance, the processing device 140A maydetermine whether the second termination condition is satisfied based onthe 1^(st) trained model, the 2^(nd) trained model, . . . , and theM^(th) trained model. An exemplary second termination condition may bethat a certain number (or count) of trained models has been producedafter the M^(th) model is trained (i.e., that M is equal to the certainnumber). The certain number may be equal to a positive integer, such as3, 4, 5, 6, etc. Another exemplary second termination condition may bethat a false positive rate of all the trained models (i.e., the 1^(st)trained model to the M^(th) trained model) is smaller than a thresholdvalue T₃.

Upon a determination that the second termination condition is satisfied,the processing device 140A may designate a trained cascaded neuralnetwork as the ROI detection model. The trained cascaded neural networkmay include the trained second model and all the trained model(s)generated before the training of the second model (i.e., the 1^(st)trained model, the 2^(nd) trained model, . . . , and the M^(th) trainedmodel). In response to a determination that the second terminationcondition is not satisfied, the processing device 140A may add a newsecond model (i.e., (M+1)^(th) model) downstream to the M^(th) trainedmodel. The processing device 140A may further train the (M+1)^(th) modeland determine whether the second termination condition is satisfiedafter a (M+1)^(th) trained model is generated. The training of thecascaded neural network may be terminated until the second terminationcondition is satisfied for a latest trained model.

It should be noted that the above description regarding the process 700is merely provided for the purposes of illustration, and not intended tolimit the scope of the present disclosure. For persons having ordinaryskills in the art, multiple variations or modifications may be madeunder the teachings of the present disclosure. However, those variationsand modifications do not depart from the scope of the presentdisclosure. In some embodiments, one or more operations may be added oromitted. For example, the processing device 140A may further test thetrained model using a set of testing samples to determine whether atesting condition is satisfied. If the testing condition is notsatisfied, the process 700 may be performed again to further train themodel.

FIG. 8 is a flowchart illustrating an exemplary process for performingROI detection on a target image using an ROI detection model accordingto some embodiments of the present disclosure. In some embodiments,process 800 may be executed by the imaging system 100. For example, theprocess 800 may be implemented as a set of instructions (e.g., anapplication) stored in a storage device (e.g., the storage device 150,the storage 220, and/or the storage 390). In some embodiments, theprocessing device 140B (e.g., the processor 210 of the computing device200, the CPU 340 of the mobile device 300, and/or one or more modulesillustrated in FIG. 4B) may execute the set of instructions and mayaccordingly be directed to perform the process 800.

In 802, the processing device 140B (e.g., the acquisition generationmodule 430, the processing circuits of the processor 210) may acquirethe target image and the ROI detection model.

The ROI detection model may refer to a neural network model that isconfigured to receive the target image as an input, and output one ormore ROIs and/or data related to the one or more ROIs in the targetimage. In some embodiments, the ROI detection model may be a trainedcascaded neural network including a plurality of sequentially connectedtrained models. The trained models may include a trained first model andat least one trained second model downstream to the trained first modelin the trained cascaded neural network. In some embodiments, the ROIdetection model may be trained by a processing device (e.g., theprocessing device 140A, the processing device 140B) by performing amethod (e.g., the process 500) for generating an ROI detection modeldisclosed herein. For example, the plurality of trained models may besequentially trained. Each trained second model may be trained using aplurality of training samples determined based on one or more trainedmodels of the plurality of trained models generated before thegeneration of the second trained model. More descriptions regarding theROI detection model may be found elsewhere in the present disclosure.See, e.g., FIG. 5 and relevant descriptions thereof. In someembodiments, at least one trained model of the ROI detection model mayinclude a multi-scale trained model configured to perform ROI detectionat a plurality of resolution levels. For example, the multi-scaletrained model may have a similar structure as a multi-scale model 1200as shown in FIG. 12 .

In some embodiments, the target image and/or the ROI detection model maybe obtained from one or more components of the imaging system 100 or anexternal source via a network (e.g., the network 120). For example, theROI detection model may be trained by a processing device (e.g., theprocessing device 140A), and stored in a storage device (e.g., thestorage device 150, the storage 220, and/or the storage 390) of theimaging system 100. The processing device 140B may access the storagedevice and retrieve the ROI detection model.

In 804, the processing device 140B (e.g., the ROI detection module 440,the processing circuits of the processor 210) may perform ROI detectionon the target image by applying the ROI detection model to the targetimage.

In some embodiments, the trained models may be configured to perform ROIdetection independently in a parallel manner. The target image and/ordata related to the target image may be inputted into each trainedmodel, and each trained model may be configured to generate an output inresponse to the input to the trained model. The output of each trainedmodel may directly form an ROI detection result of the ROI detectionmodel. Alternatively, the processing device 140B may obtain the outputof each trained model, and determine the ROI detection result (e.g., oneor more ROIs in the target image) based on the output of each trainedmodel. In some embodiments, the trained models may be configured toperform ROI detection sequentially in a serial manner. Each of thetrained models may be configured to generate an output in response to aninput to the trained model. The input to the trained first model mayinclude the target image and/or data related to the target image. Theinput to each trained second model may include an output of an upstreamtrained model connected to the trained second model. The output of alast trained model of the ROI detection model may directly form the ROIdetection result of the ROI detection model. Alternatively, theprocessing device 140B may obtain an output of the last trained model,and determine the ROI detection result (e.g., one or more ROIs in thetarget image) based on the output of the last trained model.

In some embodiments, the target image may include a plurality of targetpixels. The output of each trained model may include a first preliminaryprobability map, which includes a plurality of first preliminaryprobability values of the target pixels. Each first preliminaryprobability value may be indicative of a preliminary probability that acorresponding target pixel belongs to an ROI of the target image. In thecases in which the trained models operate in a parallel manner, theprocessing device 140B may determine a first target probability mapbased on the first preliminary probability maps outputted by the trainedmodels. The first target probability map may include a plurality offirst target probability values of the target pixels, wherein each firsttarget probability value may be indicative of a target probability thata corresponding target pixel belongs to an ROI of the target image. Forexample, for a certain target pixel, the corresponding first targetprobability value may be determined by multiplying the first preliminaryprobability value of the certain target pixel in each first preliminaryprobability map. As another example, for each trained model, theprocessing device 1406 may generate a first preliminary classificationmap based on the corresponding first preliminary probability map,wherein a target pixel having a first preliminary probability valuehigher than a threshold value T₃ is assigned with a first classificationvalue “1” in the first preliminary classification map, and a targetpixel having a first preliminary probability value lower than thethreshold value T₃ is assigned with a first classification value “0” inthe first preliminary classification map. The threshold value T₃ ofdifferent trained models may be the same or different. In someembodiments, the threshold value T₃ of a trained model may be determinedin the generation process of the trained model (e.g., in process 700 asdescribed in connection with FIG. 7 ). The first target probabilityvalue of a certain target pixel in the first target probability map maybe determined by multiplying all the first classification values of thecertain target pixel in the first preliminary classification maps. Forexample, the first target probability value of the certain target pixelmay be 0 if one or more of the first classification values are “0.” Theprocessing device 140B may further determine the one or more ROIs of thetarget image based on the first target probability map. For example, theprocessing device 140 may segment a region in the target image as an ROIof the target image, wherein the segmented region may include one ormore target pixels whose first target probability values are 1 orgreater than a threshold value T₄ (e.g., 0.8, 0.85, 0.9, 0.95).

In the cases in which that the trained models operate in a serialmanner, each trained model may determine one or more target pixels whosefirst preliminary probability values are greater than the thresholdvalue T₃ as one or more predicted ROIs and transmit the predicted ROI(s)to a next trained model for further detection. The processing device1406 may obtain the first preliminary probability map of the lasttrained model, and select one or more target pixels of the target imagewhose first preliminary probability values in the obtained firstpreliminary probability map is greater than the threshold value T₄ asthe ROI(s) of the target image.

In some embodiments, each target pixel of the target image may have aplurality of target anchor boxes enclosing the target pixel andrepresenting a candidate ROI enclosing the target pixel. A target anchorbox of a target pixel may be similar to an anchor box of a pixel of atraining image as described elsewhere in this disclosure (e.g., FIG. 5and the relevant descriptions). The output of each trained model mayinclude a second preliminary probability map and a target regressionmap. The second preliminary probability map of a trained model mayinclude a plurality of second preliminary probability values of thetarget anchor boxes. Each second preliminary probability value of atarget anchor box may be indicative of a preliminary probability that acorresponding candidate ROI is an ROI of the target image. The targetregression map may include least one target location parameter of atleast one of the target anchor boxes, each location parameter of atarget anchor box being indicative of a position of the target anchorbox relative to an ROI of the target image, or a size of the targetanchor box relative to an ROI of the target image.

In the cases in which the trained models operate in a parallel manner,the processing device 1406 may determine the ROI(s) of the target imagebased on the second preliminary probability maps and the targetregression map of the trained models. A determined ROI of the targetimage may also be referred to as a bounding box representing an ROI. Forexample, the processing device 1406 may determine a second targetprobability map including a plurality of second target probabilityvalues of the target anchor boxes based on the second preliminaryprobability maps of the trained models. Each second target probabilityvalue of a target anchor box may be indicative of a target probabilitythat a corresponding candidate ROI is an ROI of the target image. Insome embodiments, for each trained model, the processing device 140B maydetermine a second classification map including a second classificationvalue of each target anchor box in, for example, a similar manner asdetermining the first classification map as described above. Theprocessing device 140B may further determine a second target probabilityvalue of each target anchor box by multiplying a corresponding secondpreliminary probability value outputted by the last trained model andthe corresponding second classification values in all the secondclassification maps.

The processing device 140B may further determine one or more preliminaryROIs of the target image based on a target regression map of the lasttrained model and the second target probability map. For example, theprocessing device 140B may select one or more target anchor boxes whosesecond target probability values are greater than a threshold value T₅.The processing device 1406 may adjust the position and/or a size of theselected target anchor box(es) based on the target regression map of thelast trained model, wherein the adjusted target anchor box(es) may beregarded or designated as the preliminary ROI(s). For example, thetarget regression map may include a predicted distance between a targetanchor box and an ROI of the target image along a certain direction. Theprocessing device 140B may move the target anchor box by the predicteddistance along the certain direction to generate an adjusted targetanchor box (i.e., a preliminary ROI).

The processing device 140B may further determine the ROI(s) of thetarget image based on the preliminary ROI(s). In some embodiments, thepreliminary ROI(s) may include a plurality of preliminary ROIs. Theprocessing device 1406 may determine the ROI(s) of the target image byperforming a non-maximum suppressing on the preliminary ROIs to removeone or more overlapping preliminary ROIs (if any). For example, theprocessing device 140B may perform one or more iterations. In eachiteration, the processing device 1406 may rank the preliminary ROIs inthe current iteration based on the second target probability values ofthe preliminary ROIs in a descending order. For a top-ranked preliminaryROI in the ranking result, the processing device 140B may determine andremove one or more preliminary ROIs similar to the top-rankedpreliminary ROIs, e.g., a preliminary ROI whose IOU with the top-rankedpreliminary ROI is greater than a threshold IOU. The processing device140B may designate the top-ranked preliminary ROI as an ROI of thetarget image. If there are a plurality of remaining preliminary ROIs,the processing device 140B and designate the remaining preliminary ROIsas the preliminary ROIs in a next iteration and proceed to the nextiteration. In some embodiments, the preliminary ROI(s) may be directlydesignated as the ROI(s) of the target image without processing.

In the cases in which that the trained models operate in a serialmanner, each trained model may determine one or more target anchor boxeswhose second preliminary probability values are greater than a thresholdvalue T₆ as one or more predicted ROIs and transmit the predicted ROI(s)to a next trained model (e.g., the immediately downstream trained model)for further detection. The processing device 1406 may determine theROI(s) of the target image based on the second preliminary probabilitymap and the target regression map outputted by the last trained model.For example, the processing device 1406 may determine one or morepreliminary ROIs based on the second preliminary probability map and thetarget regression map outputted by the last trained model. Theprocessing device 140B may then determine the ROI(s) of the target imagebased on the preliminary ROI(s), for example, by performing anon-maximum suppressing on the preliminary ROI(s). The ROI(s) of thetarget image may be determined based on the second preliminaryprobability map and the target regression map of the last trained modelin a similar manner as how the ROI(s) of the target image is determinedbased on the target regression map of the last trained model and thesecond target probability map.

In some embodiments, the ROI detection result may include one or moreROIs of the target image determined by the processing device 140B asdescribed above. An ROI of the target image may be represented orcharacterized by position information, size information, shapeinformation of the ROI, or the like, or any combination thereof. Forexample, the ROI of the target image may be represented or characterizedby a coordinate of central point (or each target pixel) of the ROI and asize of the ROI. In some embodiments, the ROI detection result may bedetermined by the processing device 140 based on the output of the ROIdetection model as described above. Optionally, the one or more ROIs mayinclude a plurality of ROIs, and the processing device 140 maypostprocess the ROIs to generate the ROI detection result. For example,the processing device 140 may remove one or more noise points, such as apixel in a non-ROI surrounded by pixels in an ROI, a pixel in an ROIsurrounded by pixels in a non-ROI, or the like, or any combinationthereof. As another example, the processing device 140 may perform aconnected-component analysis to determine one or more large connectedregions (e.g., a region having a size greater than a first thresholdsize) formed by ROIs and/or remove one or more small connected regions(e.g., a region having a size smaller than a second threshold size)formed by ROIs, wherein the large connected region(s) may be outputtedin the ROI detection result. In some alternative embodiments, the ROIdetection model may include one or more additional components (e.g., asoftmax function) configured to determine the ROI detection result basedon the output of each trained model of the ROI detection model. In sucha case, the ROI detection model may direct output the ROI detectionresult of the target image.

According to some embodiments of the present disclosure, the trainedmodels of the ROI detection model may be trained sequentially. Eachtrained model may be generated based on different training samples andhave different ROI detection accuracies. The trained models may beapplied parallel or sequentially to detect the ROI(s) in the targetimage. The detected ROI(s) may need to be verified by each trainedmodel. For example, a target pixel may be regarded as a pixel of an ROIonly if each trained model predicts that the target pixel is a pixel inan ROI of the target image. This may improve the accuracy of the ROIdetection result.

It should be noted that the above description of the process 800 ismerely provided for the purposes of illustration, and not intended tolimit the scope of the present disclosure. For persons having ordinaryskills in the art, multiple variations and modifications may be madeunder the teachings of the present disclosure. However, those variationsand modifications do not depart from the scope of the presentdisclosure. In some embodiments, the operations of the process 800 areintended to be illustrative. The process 800 may be accomplished withone or more additional operations not described and/or without one ormore of the operations herein discussed. Additionally, the order inwhich the operations of the process 800 described above is not intendedto be limiting. For example, the process 800 may include an additionaloperation in which the processing device 140B transmits the ROIdetection result to a terminal device for display.

FIG. 9 is a schematic diagram illustrating an exemplary ROI detectionmodel 900 according to some embodiments of the present disclosure. Asshown in FIG. 9 , the ROI detection model 900 may be a trained cascadedneural network including M sequentially connected trained models, i.e.,a trained 1^(st) model, a trained 2^(nd) model, a trained 3^(rd) model,. . . , and a trained M^(th) model.

The ROI detection model 900 may be an exemplary ROI detection model asdescribed in connection with FIG. 8 , which is configured to perform ROIdetection on a target image. The trained models of the ROI detectionmodel 900 may be configured to perform ROI detection sequentially. Theinput to the trained 1^(st) model may include the target image, theinput to the trained 2^(nd) model may include an output of the trained1st model, the input to the trained 3^(rd) model may include an outputof the trained 2^(nd) model, . . . , and the input to the trained M^(th)model may include an output of the trained (M−1)^(th) model. The one ormore ROIs of the target image may be determined based on an output ofthe trained M^(th) model. In some embodiments, the output of eachtrained model may include one or more predicted ROIs in the target imageas shown in FIG. 9 . The predicted ROIs may include one or more targetpixels or target anchor boxes of the target image. For a specifictrained model, the one or more predicted ROIs outputted by the specifictrained model may be transmitted to a downstream trained model forfurther verification, wherein a portion of the one or more predictedROIs may be verified by the downstream trained model as predicted ROIsas well, while the other portion of the one or more predicted ROIs maybe determined as non-ROIs by the downstream trained model.

FIG. 10 is a schematic diagram illustrating an exemplary process forperforming lesion detection in a target image 1002 using a lesiondetection model 1000 according to some embodiments of the presentdisclosure.

The lesion detection model 1000 is an exemplary ROI detection model asdescribed in connection with FIG. 8 . The target image 1002 is a CTimage of a chest with one or more pulmonary nodules. As shown in FIG. 10, the lesion detection model 1000 includes a trained model M₁, a trainedmodel M₂, and a trained model M₃. The target image 1002 was inputtedinto the trained model M₁. The trained model M₁ identified a pluralityof predicted lesion areas 1004 and a plurality of predicted non-lesionareas 1010 from the target image. Each predicted lesion area 1004 may berepresented by a block (which includes one or more of pixels) of thetarget image. The predicted lesion areas 1004 were inputted into thetrained model M₂ for further detection, while the predicted non-lesionareas 1010 were omitted from further detection. The trained model M₂identified a plurality of predicted lesion areas 1006 and a plurality ofpredicted non-lesion areas 1012 from the predicted lesion areas 1004.The predicted lesion areas 1006 were inputted into the trained model M₃for further detection, while the predicted non-lesion areas 1012 wereomitted from further detection. The trained model M₃ further identifieda plurality of non-lesion areas 1014 and a plurality of lesion areas1008 from the predicted lesion areas 1006. The predicted lesion areas1008 were designated as a plurality of lesion areas of the target image1002.

As shown in FIG. 10 , a predicted lesion area enclosed by a solid boxrepresents a true lesion area, and a predicted lesion area enclosed by adotted box represents a false lesion area. The trained model M₃ weregenerated based on one or more false positive samples of the trainedmodels M₁ and M₂, and therefore more reliable in distinguishing anon-lesion from a lesion than the trained models M₁ and M₂. The falselesion areas of the trained model M₁ and M₂ were further verified andremoved by the trained model M₃. It is indicated that, compared withusing a single trained model (e.g., the trained model M₁ or M₂), usingthe lesion detection model 1000 may improve accuracy of lesion detectionand avoid misdiagnosis.

It should be noted that the examples in FIGS. 9 and 10 are merelyprovided for the purposes of illustration, and not intended to limit thescope of the present disclosure. For persons having ordinary skills inthe art, multiple variations and modifications may be made under theteachings of the present disclosure. However, those variations andmodifications do not depart from the scope of the present disclosure.For example, the trained models of the ROI detection model 900 mayperform ROI detection in a parallel manner as described in connectionwith operation 804. As another example, the ROI detection model 900 andthe lesion detection model 1000 may include any number of trainedmodels.

FIG. 11 is a schematic diagram illustrating an exemplary single-scalemodel 1100 according to some embodiments of the present disclosure.

The single-scale model 1100 may be configured to perform ROI detectionin an image 1101 at a single resolution level. As shown in FIG. 11 , thesingle-scale model 1100 includes four sequentially connected layers,i.e., layers 1102, 1104, 1106, and 1108. Each layer includes a neuralnetwork block for feature extraction. A layer other than the layer 1108is connected to a next layer via a first downsampling path. The firstdownsampling path may refer to a path of the single-scale model 1100that connects the layers 1102 to 1108, along which information (e.g., anoutput of a specific layer) may be downsampled. For example, the layer1102 may receive the image 1101 as an input and generate an output byprocessing the image, wherein the output of the layer 1102 isdownsampled (e.g., downsampled using a max pooling operator) and thedownsampled output is transmitted to the layer 1104. An ROI detectionresult 1110 may be outputted by the layer 1108. Because of the firstdownsampling path, the ROI detection result 1110 may correspond to alower resolution than the image 1101, which may result in a loss ofhigh-resolution image information and/or an undetected ROI due to itssmall size (e.g., an ROI having a size smaller than the resolution ofROI detection result 1110).

FIG. 12 is a schematic diagram illustrating an exemplary multi-scalemodel 1200 according to some embodiments of the present disclosure.

The multi-scale model 1200 (referred to as a model 1200 for brevity) maybe configured to perform ROI detection in an image 1201 at a pluralityof resolution levels. In some embodiments, the model 1200 may be acomponent of an ROI detection model (e.g., the ROI detection model 900).

As shown in FIG. 12 , the model 1200 may include four layers (i.e.,layers 1202, 1204, 1206, and 1208). The layer 1202 may also be referredto as a first layer of the model 1200, the layer 1208 may also bereferred to as a last layer of the model 1200, and the layers 1204 and1206 may also be referred to as middle layers of the model 1200. Eachlayer of the model 1200 other than the layer 1208 (i.e., the last layer)is connected to a next layer via a second downsampling path. The seconddownsampling path may refer to a path in the model 1200 that connectsblocks 1203, 1204A, 1206A, and 1209, along which information (e.g., anoutput of a specific block) may be downsampled. Each layer other thanthe layer 1202 (i.e., the first layer) and the layer 1204 is connectedto a previous layer via an upsampling path. The upsampling path mayrefer to a path in the model 1200 that connects blocks 1209, 1204A,1206B, and 1204B, along which information (e.g., an output of a specificblock) may be upsampled. Each of the layers 1204 to 1208 may correspondto one of the resolution levels and configured to generate an ROIdetection result at the corresponding resolution level.

The layer 1202 includes a block 1203. The layer 1204 includes a block1204A, a block 12046, and a skip connection S₁ connecting the blocks1204A and 12046. The layer 1206 includes a block 1206A, a block 1206B,and a skip connection S₂ connecting the blocks 1206A and 12066. Thelayer 1208 includes a block 1209. A block of a layer may be a neuralnetwork component used for feature extraction, such as one or moreconvolution operators and/or a neural network model (e.g., a residualnetwork). Different layers of the model 1200 may be of the same type ordifferent types of blocks. A skip connection connecting two blocks maybe configured to connect the two blocks, for example, transmitting anoutput of one of the blocks to the other block. Taking the layer 1204 asan instance, the skip connection S₁ may transmit a feature vectoroutputted by the block 1204A to the block 12046. It should be noted thatthe skip connection S₁ and S₂ are provided for illustration purposes,and may be replaced by any other connection component that can be usedto connect a plurality of blocks.

In operation, the image 1201 is inputted into the block 1203 of thelayer 1202, wherein the block 1203 may generate an output (e.g., afeature map or a feature vector) by processing the image 1201. Theoutput of the block 1203 may be downsampled and the downsampled outputmay be transmitted to the block 1204A of the layer 1204 for furtheranalysis. In some embodiments, the downsampling of the output of theblock 1203 may be performed by a max pooling operator. Similarly, anoutput of the block 1204A and an output of the block 1206A may bedownsampled and transmitted to the block 1206A and the block 1209,respectively. An output of the block 1209 may be upsampled andtransmitted to the block 12066 of the layer 1206. Similarly, an outputof the block 12066 may be upsampled and transmitted to the block 12046of the layer 1204. In the layer 1204, the block 1204A may extract one ormore features from the downsampled output of the block 1203. Thefeature(s) extracted by the block 1204A may be transmitted to the block12046 via the skip connection S₁. The feature(s) extracted by the block1204A in combination with the upsampled output of the block 12066 mayserve as an input to the block 12046. The block 12046 may extract one ormore features based on the input. The feature(s) extracted by the block1204A may provide more detailed information of the image 1201 (or alsoreferred to as information at a fine scale). The upsampled output of theblock 12066 may provide more global information of the image 1201 (oralso referred to as information at a coarse scale). The input of theblock 1204B may include both the detailed information and the globalinformation of the image 1201, thereby the feature(s) extracted by theblock 12046 may provide more comprehensive information of the image1201. The layer 1204 may further generate an ROI detection result 1210based on the feature(s) generated by the block 12046. Similar to thelayer 1204, the layer 1206 may generate an ROI detection result 1212.The layer 1208 may generate an ROI detection result 1214 based on anoutput of the block 1209. The layers 1204, 1206, and 1208 may correspondto different resolution levels and have different detection accuraciesregarding ROIs of different sizes. For example, the layer 1204 may havea higher accuracy in detecting small ROIs, and the layer 1208 may have ahigher accuracy in detecting large ROIs. As such, the model 1200 maydetect ROIs of different sizes and have a higher ROI detection accuracythan a single-scale model (e.g., the single-scale model 1100).

It should be noted that the examples illustrated in FIGS. 11 and 12 areprovided for the purposes of illustration, and is not intended to limitthe scope of the present disclosure. For persons having ordinary skillsin the art, multiple variations and modifications may be made under theteachings of the present disclosure. However, those variations andmodifications do not depart from the scope of the present disclosure.For example, the model 1200 may include any number of layers. Each layermay include any number of blocks and/or skip connections. As anotherexample, the model 1200 may include one or more additional componentsand/or one or more components illustrated in FIG. 12 may be omitted. Insome embodiments, an ROI detection result outputted by a layer of themodel 1200 may include a probability map and/or a regression map asdescribed elsewhere in this disclosure (e.g., FIG. 8 and the relevantdescriptions).

FIG. 13 is a schematic diagram illustrating an exemplary CNN model 1300according to some embodiments of the present disclosure. In someembodiments, the CNN model 1300 may be a component of an ROI detectionmodel as described elsewhere in this disclosure (e.g., FIGS. 5 and 8 andthe relevant descriptions)

As shown in FIG. 13 , the CNN model 1300 may include an input layer1302, a plurality of hidden layers 1304, and an output layer 1306. Thehidden layers 1304 may include one or more convolutional layers, one ormore rectified linear unit (ReLU) layers, one or more pooling layers,one or more fully connected layer, or the like, or any combinationthereof. For illustration purposes, exemplary hidden layers 1304,including a convolutional layer 1304-1, a pooling layer 1304-2, and afully connected layer 1304-N, are provided in FIG. 13 .

In some embodiments, an image (e.g., a training image, a target image)may be inputted into the CNN model 1300. The image may be represented asa 2D matrix or a 3D matrix including a plurality of elements (e.g.,pixels or voxels). Each of the plurality of elements in the matrix mayhave a value representing a feature or characteristic of the element.

The convolutional layer 1304-1 may include a plurality of kernels (e.g.,A, B, C, and D), which may be used to extract a feature of the image. Insome embodiments, each kernel of the plurality of kernels may filter aportion of the image to generate a specific feature corresponding to theportion. The specific feature may be determined based on the kernels.Exemplary features may include a low-level feature (e.g., an edgefeature, a textural feature), a high-level feature, or a complicatedfeature.

The pooling layer 1304-2 may take an output of the convolutional layer1304-1 as an input. The pooling layer 1304-2 may include a plurality ofpooling nodes (e.g., E, F, G, and H), which may be used to sample theoutput of the convolutional layer 1304-1, so as to reduce thecomputational load of data processing and accelerate the speed of dataprocessing speed. In some embodiments, a size of the matrix representingthe image may be reduced in the pooling layer 1304-2.

The fully connected layer 1304-N may include a plurality of neurons(e.g., O, P, M, and N). The neurons may be connected to the poolingnodes in the pooling layer 1304-2. In the fully connected layer 1304-N,a plurality of vectors corresponding to the plurality of pooling nodesmay be determined based on one or more features of the image, and aplurality of weighting coefficients may be assigned to the plurality ofvectors.

The output layer 1306 may determine an output based on the vectors andthe weighting coefficients obtained from the fully connected layer1304-N. In some embodiments, an output of the output layer 1306 mayinclude a probability map, a classification map, and/or a regression mapas described elsewhere in this disclosure (e.g., FIGS. 5 and 8 and therelevant descriptions).

In some embodiments, the CNN model may be implemented on one or moreprocessing devices (e.g., the processing device 140, the processor 210of the computing device 200). In some embodiments, a plurality ofprocessing devices may execute a parallel processing operation in somelayers of the CNN model 1300 by, for example, assigning two or moreprocessing devices for an operation of different nodes (e.g., a kernel,a pooling node, a neuron) in the CNN model 1300. For example, a firstGPU may execute the operation corresponding to the kernel A and kernelB, and a second kernel may execute the operation corresponding to thekernel C and kernel D. Similarly, a plurality of GPUs may also executethe operation of other nodes (e.g., a kernel, a pooling node, a neuron)in the CNN model 1300. In addition, in some embodiments, a storagedevice (e.g., the storage device 150, the storage 220 of the computingdevice 200) may be provided for storing data related to the CNN model1300, such as activations and learned weights for each node.

It should be noted that the example in FIG. 13 is merely provided forthe purposes of illustration, and not intended to limit the scope of thepresent disclosure. For persons having ordinary skills in the art,multiple variations and modifications may be made under the teachings ofthe present disclosure. However, those variations and modifications donot depart from the scope of the present disclosure. For example, theCNN model 1300 may include one or more additional components.Additionally or alternatively, one or more components of the CNN model1300 described above may be omitted. As another example, the CNN model1300 may include any number of layers and nodes.

It will be apparent to those skilled in the art that various changes andmodifications can be made in the present disclosure without departingfrom the spirit and scope of the disclosure. In this manner, the presentdisclosure may be intended to include such modifications and variationsif the modifications and variations of the present disclosure are withinthe scope of the appended claims and the equivalents thereof.

Having thus described the basic concepts, it may be rather apparent tothose skilled in the art after reading this detailed disclosure that theforegoing detailed disclosure is intended to be presented by way ofexample only and is not limiting. Various alterations, improvements, andmodifications may occur and are intended to those skilled in the art,though not expressly stated herein. These alterations, improvements, andmodifications are intended to be suggested by this disclosure, and arewithin the spirit and scope of the exemplary embodiments of thisdisclosure.

Moreover, certain terminology has been used to describe embodiments ofthe present disclosure. For example, the terms “one embodiment,” “anembodiment,” and “some embodiments” mean that a particular feature,structure or characteristic described in connection with the embodimentis included in at least one embodiment of the present disclosure.Therefore, it is emphasized and should be appreciated that two or morereferences to “an embodiment” or “one embodiment” or “an alternativeembodiment” in various portions of this specification are notnecessarily all referring to the same embodiment. Furthermore, theparticular features, structures or characteristics may be combined assuitable in one or more embodiments of the present disclosure.

Further, it will be appreciated by one skilled in the art, aspects ofthe present disclosure may be illustrated and described herein in any ofa number of patentable classes or context including any new and usefulprocess, machine, manufacture, or composition of matter, or any new anduseful improvement thereof. Accordingly, aspects of the presentdisclosure may be implemented entirely hardware, entirely software(including firmware, resident software, micro-code, etc.) or combiningsoftware and hardware implementation that may all generally be referredto herein as a “module,” “unit,” “component,” “device,” or “system.”Furthermore, aspects of the present disclosure may take the form of acomputer program product embodied in one or more computer readable mediahaving computer readable program code embodied thereon.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including electro-magnetic, optical, or thelike, or any suitable combination thereof. A computer readable signalmedium may be any computer readable medium that is not a computerreadable storage medium and that may communicate, propagate, ortransport a program for use by or in connection with an instructionexecution system, apparatus, or device. Program code embodied on acomputer readable signal medium may be transmitted using any appropriatemedium, including wireless, wireline, optical fiber cable, RF, or thelike, or any suitable combination of the foregoing.

Computer program code for carrying out operations for aspects of thepresent disclosure may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Scala, Smalltalk, Eiffel, JADE, Emerald, C++, C#, VB. NET,Python or the like, conventional procedural programming languages, suchas the “C” programming language, Visual Basic, Fortran 2003, Perl, COBOL2002, PHP, ABAP, dynamic programming languages such as Python, Ruby andGroovy, or other programming languages. The program code may executeentirely on the user's computer, partly on the user's computer, as astand-alone software package, partly on the user's computer and partlyon a remote computer or entirely on the remote computer or server. Inthe latter scenario, the remote computer may be connected to the user'scomputer through any type of network, including a local area network(LAN) or a wide area network (WAN), or the connection may be made to anexternal computer (for example, through the Internet using an InternetService Provider) or in a cloud computing environment or offered as aservice such as a Software as a Service (SaaS).

Furthermore, the recited order of processing elements or sequences, orthe use of numbers, letters, or other designations therefore, is notintended to limit the claimed processes and methods to any order exceptas may be specified in the claims. Although the above disclosurediscusses through various examples what is currently considered to be avariety of useful embodiments of the disclosure, it is to be understoodthat such detail is solely for that purpose, and that the appendedclaims are not limited to the disclosed embodiments, but, on thecontrary, are intended to cover modifications and equivalentarrangements that are within the spirit and scope of the disclosedembodiments. For example, although the implementation of variouscomponents described above may be embodied in a hardware device, it mayalso be implemented as a software only solution, e.g., an installationon an existing server or mobile device.

Similarly, it should be appreciated that in the foregoing description ofembodiments of the present disclosure, various features are sometimesgrouped together in a single embodiment, figure, or description thereoffor the purpose of streamlining the disclosure aiding in theunderstanding of one or more of the various embodiments. This method ofdisclosure, however, is not to be interpreted as reflecting an intentionthat the claimed subject matter requires more features than areexpressly recited in each claim. Rather, claim subject matter lie inless than all features of a single foregoing disclosed embodiment.

In some embodiments, the numbers expressing quantities or propertiesused to describe and claim certain embodiments of the application are tobe understood as being modified in some instances by the term “about,”“approximate,” or “substantially.” For example, “about,” “approximate,”or “substantially” may indicate a certain variation (e.g., ±1%, ±5%,±10%, or ±20%) of the value it describes, unless otherwise stated.Accordingly, in some embodiments, the numerical parameters set forth inthe written description and attached claims are approximations that mayvary depending upon the desired properties sought to be obtained by aparticular embodiment. In some embodiments, the numerical parametersshould be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques. Notwithstandingthat the numerical ranges and parameters setting forth the broad scopeof some embodiments of the application are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspracticable. In some embodiments, a classification condition used inclassification is provided for illustration purposes and modifiedaccording to different situations. For example, a classificationcondition that “a probability value is greater than the threshold value”may further include or exclude a condition that “the probability valueis equal to the threshold value”.

What is claimed is:
 1. A region of interest (ROI) detection system,comprising: at least one storage device including a set of instructions;and at least one processor configured to communicate with the at leastone storage device, wherein when executing the set of instructions, theat least one processor is configured to direct the system to performoperations including: acquiring a target image and an ROI detectionmodel; and performing ROI detection on the target image by applying theROI detection model to the target image, the ROI detection modelincluding a multi-scale trained model configured to perform the ROIdetection at a plurality of resolution levels, wherein the multi-scaletrained model includes a plurality of sequentially connected layershaving different detection accuracies regarding ROIs of different sizes,and each of the plurality of layers corresponds to one of the pluralityof resolution levels and is configured to generate an ROI detectionresult at the corresponding resolution level.
 2. The system of claim 1,wherein the plurality of layers includes a first layer, a last layer,and one or more middle layers between the first layer and the lastlayer, at least one layer of the plurality of layers other than the lastlayer is connected to a next layer via a downsampling path, and at leastone layer of the plurality of layers other than the first layer isconnected to a previous layer via an upsampling path.
 3. The system ofclaim 2, wherein at least one of the one or more middle layers comprisesa first block, a second block, and a connection component connecting thefirst block and the second block.
 4. The system of claim 3, wherein theconnection component includes a skip connection.
 5. The system of claim4, wherein the first block of the at least one middle layer obtainsinformation of the target image at a fine scale by the upsampling path,the second block of the at least one middle layer obtains information ofthe target image at a coarse scale by the downsampling path, and the ROIdetection result generated by the at least one middle layer includesinformation at the fine scale and the coarse scale.
 6. The system ofclaim 3, wherein the first block of the at least one middle layer isconnected to other blocks in other layers via a downsampling path, andthe second block of the at least one middle layer is connected to atleast one other block in at least one other layer via an upsamplingpath.
 7. The system of claim 1, wherein the ROI detection model is atrained cascaded neural network including a plurality of sequentiallyconnected trained models, the plurality of trained models include atrained first model and at least one trained second model downstream tothe trained first model in the trained cascaded neural network, theplurality of trained models are sequentially trained, and each of the atleast one trained second model is trained using a plurality of trainingsamples determined based on one or more trained models of the pluralityof trained models generated before the generation of the trained secondmodel.
 8. The system of claim 7, wherein at least one trained model ofthe plurality of sequentially connected trained models includes themulti-scale trained model.
 9. The system of claim 7, wherein: each ofthe plurality of sequentially connected trained models is configured togenerate an output in response to an input of the trained model, theinput to the trained first model includes the target image, the input toeach of the at least one trained second model includes an output of aprevious trained model connected to the trained second model, and toperform an ROI detection on the target image by applying the ROIdetection model to the target image, the at least one processor isfurther configured to direct the system to perform additional operationsincluding: obtaining an output of a last trained model of the pluralityof sequentially connected trained models; and determining, based on theoutput of the last trained model, one or more ROIs in the target image.10. The system of claim 7, wherein: each of the plurality ofsequentially connected trained models is configured to generate anoutput in response to an input of the trained model, the input to eachtrained model includes the target image, and to perform an ROI detectionon the target image by applying the ROI detection model to the targetimage, the at least one processor is further configured to direct thesystem to perform additional operations including: obtaining an outputof each of the plurality of sequentially connected trained models; anddetermining, based on the outputs of the plurality of sequentiallyconnected trained models, one or more ROIs in the target image.
 11. Thesystem of claim 10, wherein: the target image includes a plurality oftarget pixels, the output of each trained model includes a firstpreliminary probability map, and to determine one or more ROIs in thetarget image based on the outputs of the plurality of trained models,the at least one processor is further configured to direct the system toperform additional operations including: determining, based on the firstpreliminary probability maps, a first target probability map; anddetermining, based on the first target probability map, the one or moreROIs of the target image.
 12. The system of claim 10, wherein: thetarget image includes a plurality of target pixels, each of the targetpixels having a plurality of target anchor boxes, each of the targetanchor boxes enclosing the target pixel and representing a candidate ROIenclosing the target pixel; the output of each trained model includes asecond preliminary probability map and a target regression map, and todetermine one or more ROIs in the target image based on the outputs ofthe plurality of sequentially connected trained models, the at least oneprocessor is further configured to direct the system to performadditional operations including: determining, based on the secondpreliminary probability maps from the plurality of sequentiallyconnected trained models, a second target probability map; determining,based on the target regression map of a last trained model of theplurality of sequentially connected trained models and the second targetprobability map, a plurality of preliminary ROIs of the target image;and determining, based on the plurality of preliminary ROIs, the one ormore ROIs of the target image.
 13. The system of claim 7, wherein theROI detection model is generated by: acquiring a plurality of trainingimages, each of the plurality of training images being annotated withone or more ROIs; and generating an ROI detection model by training acascaded neural network using the plurality of training images, thecascaded neural network including a plurality of sequentially connectedmodels, wherein: the plurality of models include a first model and atleast one second model downstream to the first model in the cascadedneural network, the training the cascaded neural network comprisessequentially training the plurality of models, and training each of theplurality of models comprises: determining, based at least in part onthe plurality of training images, a plurality of training samples of themodel; and generating a trained model by training the model using theplurality of training samples of the model, wherein the plurality oftraining samples of each of the at least one second model are determinedfurther based on one or more trained models generated before thetraining of the second model.
 14. The system of claim 13, wherein thedetermining a plurality of training samples of the first modelcomprises: determining, based on the plurality of training images, aplurality of first negative samples and a plurality of positive samples,each of the plurality of first negative samples being indicative of atleast a portion of a non-ROI in the plurality of training images, eachof the plurality of positive samples being indicative of at least aportion of the ROIs in the plurality of training images; and designatingthe plurality of first negative samples and the plurality of positivesamples as the training samples of the first model.
 15. The system ofclaim 14, wherein the determining the plurality of first negativesamples and the plurality of positive samples comprises: for each of aplurality of pixels in the plurality of training images, defining one ormore anchor boxes enclosing the pixel, each of the one or more anchorboxes representing a candidate ROI enclosing the pixel; comparing theanchor boxes with the ROIs of the plurality of training images togenerate a comparison result; and determining, among the anchor boxesbased on the comparison result, the plurality of first negative samplesand the plurality of positive samples.
 16. The system of claim 14,wherein the determining the training samples for each of the at leastone second model comprises: for each of the at least one second model,determining a plurality of predicted positive samples representing aplurality of predicted ROIs in the plurality of training images byapplying the one or more trained models generated before the training ofthe second model to the plurality of training images; identifying, amongthe plurality of predicted positive samples, one or more false positivesamples; determining a plurality of second negative samples of thesecond model, the plurality of second negative samples including atleast a portion of the one or more false positive samples; anddesignating the plurality of second negative samples and the pluralityof positive samples as the training samples of the second model.
 17. Amethod implemented on a computing device including at least oneprocessor, at least one storage medium, and a communication platformconnected to a network, the method comprising: acquiring a target imageand an ROI detection model; and performing ROI detection on the targetimage by applying the ROI detection model to the target image, the ROIdetection model including a multi-scale trained model configured toperform the ROI detection at a plurality of resolution levels, whereinthe multi-scale trained model includes a plurality of sequentiallyconnected layers having different detection accuracies regarding ROIs ofdifferent sizes, and each of the plurality of layers corresponds to oneof the plurality of resolution levels and is configured to generate anROI detection result at the corresponding resolution level.
 18. Themethod of claim 17, wherein the plurality of layers includes a firstlayer, a last layer, and one or more middle layers between the firstlayer and the last layer, at least one layer of the plurality of layersother than the last layer is connected to a next layer via adownsampling path, and at least one layer of the plurality of layersother than the first layer is connected to a previous layer via anupsampling path.
 19. The method of claim 18, wherein at least one of theone or more middle layers comprises a first block, a second block, and aconnection component connecting the first block and the second block.20. A non-transitory computer-readable storage medium includinginstructions that, when accessed by at least one processor of a regionof interest (ROI) detection system, causes the system to perform amethod, the method comprising: acquiring a target image and an ROIdetection model; and performing ROI detection on the target image byapplying the ROI detection model to the target image, the ROI detectionmodel including a multi-scale trained model configured to perform theROI detection at a plurality of resolution levels, wherein themulti-scale trained model includes a plurality of sequentially connectedlayers having different detection accuracies regarding ROIs of differentsizes, and each of the plurality of layers corresponds to one of theplurality of resolution levels and is configured to generate an ROIdetection result at the corresponding resolution level.